diff --git a/edit.html b/edit.html
index 12614c99..b87396fe 100644
--- a/edit.html
+++ b/edit.html
@@ -91,7 +91,6 @@
     <script src="edit/colorpicker-helper.js"></script>
     <script src="edit/beautify.js"></script>
     <script src="edit/show-keymap-help.js"></script>
-    <script src="edit/refresh-on-view.js"></script>
     <script src="edit/codemirror-themes.js"></script>
 
     <script src="edit/source-editor.js"></script>
@@ -305,7 +304,7 @@
       </section>
       <section id="actions">
         <div>
-          <button id="save-button" i18n-text="styleSaveLabel" data-hotkey-tooltip="save"></button>
+          <button id="save-button" i18n-text="styleSaveLabel" data-hotkey-tooltip="save" disabled></button>
           <button id="beautify" i18n-text="styleBeautify"></button>
           <a href="manage.html" tabindex="-1"><button id="cancel-button" i18n-text="styleCancelEditLabel"></button></a>
         </div>
diff --git a/edit/codemirror-default.css b/edit/codemirror-default.css
index 6adbf962..0db190f4 100644
--- a/edit/codemirror-default.css
+++ b/edit/codemirror-default.css
@@ -15,8 +15,7 @@
   -webkit-animation: highlight 3s cubic-bezier(.18, .02, 0, .94);
 }
 .CodeMirror-focused {
-  outline: -webkit-focus-ring-color auto 5px;
-  outline-offset: -2px;
+  outline: #7dadd9 auto 1px; /* not using the ring-color hack as it became ugly in new Chrome */
 }
 .CodeMirror-bookmark {
   background: linear-gradient(to right, currentColor, transparent);
@@ -24,13 +23,6 @@
   width: 2em;
   opacity: .5;
 }
-@supports (-moz-appearance:none) {
-  /* restrict to FF */
-  .CodeMirror-focused {
-    outline: #7dadd9 auto 1px;
-    outline-offset: -1px;
-  }
-}
 .CodeMirror-search-field {
   width: 10em;
 }
diff --git a/edit/edit.css b/edit/edit.css
index 3635fa61..8db215ba 100644
--- a/edit/edit.css
+++ b/edit/edit.css
@@ -63,6 +63,7 @@ label {
 #sections {
   padding-left: 280px;
   min-height: 0;
+  height: 100%;
 }
 #sections h2 {
   margin-top: 1rem;
@@ -278,12 +279,6 @@ input:invalid {
 .section-editor .section:not(:first-child) {
   border-top: 2px solid hsl(0, 0%, 80%);
 }
-.section-editor:not(.section-editor-ready) .section {
-  opacity: 0 !important;
-}
-.section-editor:not(.section-editor-ready) .CodeMirror {
-  height: 0;
-}
 .add-section:after {
   content: attr(short-text);
 }
@@ -817,13 +812,8 @@ body.linter-disabled .hidden-unless-compact {
   color: #888;
 }
 
-/* FIXME: remove the ID selector */
-#sections .single-editor {
+.single-editor {
   height: 100%;
-  margin: 0;
-  padding: 0;
-  display: flex;
-  box-sizing: border-box;
 }
 
 .single-editor .CodeMirror {
@@ -843,7 +833,6 @@ body.linter-disabled .hidden-unless-compact {
 }
 
 .usercss.firefox #sections,
-.usercss.firefox .single-editor,
 .usercss.firefox .CodeMirror {
   height: 100%;
 }
@@ -996,7 +985,7 @@ body.linter-disabled .hidden-unless-compact {
     flex-direction: column;
     flex: 1;
   }
-  #sections > * {
+  #sections > :not(.single-editor) {
     margin: 0 .5rem;
     padding: .5rem 0;
   }
diff --git a/edit/edit.js b/edit/edit.js
index 7d3b49d4..b902a1e3 100644
--- a/edit/edit.js
+++ b/edit/edit.js
@@ -541,7 +541,7 @@ function detectLayout() {
           body.classList.add('fixed-header');
         }
       }, 250);
-      window.addEventListener('scroll', fixedHeader);
+      window.addEventListener('scroll', fixedHeader, {passive: true});
     }
   } else {
     body.classList.remove('compact-layout');
diff --git a/edit/refresh-on-view.js b/edit/refresh-on-view.js
deleted file mode 100644
index ffbc0589..00000000
--- a/edit/refresh-on-view.js
+++ /dev/null
@@ -1,29 +0,0 @@
-/* global CodeMirror */
-/*
-Initialization of the multi-sections editor is slow if there are many editors
-e.g. https://github.com/openstyles/stylus/issues/178. So we only refresh the
-editor when they were scroll into view.
-*/
-'use strict';
-
-CodeMirror.defineExtension('refreshOnView', function () {
-  const cm = this;
-  if (typeof IntersectionObserver === 'undefined') {
-    // uh
-    cm.isRefreshed = true;
-    cm.refresh();
-    return;
-  }
-  const wrapper = cm.display.wrapper;
-  const observer = new IntersectionObserver(entries => {
-    for (const entry of entries) {
-      if (entry.isIntersecting) {
-        // wrapper.style.visibility = 'visible';
-        cm.isRefreshed = true;
-        cm.refresh();
-        observer.disconnect();
-      }
-    }
-  });
-  observer.observe(wrapper);
-});
diff --git a/edit/sections-editor-section.js b/edit/sections-editor-section.js
index 8885cfc6..2735ac2c 100644
--- a/edit/sections-editor-section.js
+++ b/edit/sections-editor-section.js
@@ -296,19 +296,14 @@ function createSection({
 
   function insertApplyAfter(init, base) {
     const apply = createApply(init);
-    if (base) {
-      const index = appliesTo.indexOf(base);
-      appliesTo.splice(index + 1, 0, apply);
-      appliesToContainer.insertBefore(apply.el, base.el.nextSibling);
-    } else {
-      appliesTo.push(apply);
-      appliesToContainer.appendChild(apply.el);
-    }
+    appliesTo.splice(base ? appliesTo.indexOf(base) + 1 : appliesTo.length, 0, apply);
+    appliesToContainer.insertBefore(apply.el, base ? base.el.nextSibling : null);
     dirty.add(apply, apply);
     if (appliesTo.length > 1 && appliesTo[0].all) {
       removeApply(appliesTo[0]);
     }
     emitSectionChange();
+    return apply;
   }
 
   function removeApply(apply) {
@@ -380,7 +375,8 @@ function createSection({
     }
     $('.add-applies-to', el).addEventListener('click', e => {
       e.preventDefault();
-      insertApplyAfter({type, value: ''}, apply);
+      const newApply = insertApplyAfter({type, value: ''}, apply);
+      $('input', newApply.el).focus();
     });
 
     return apply;
diff --git a/edit/sections-editor.js b/edit/sections-editor.js
index bcf95148..8a04e06c 100644
--- a/edit/sections-editor.js
+++ b/edit/sections-editor.js
@@ -29,6 +29,9 @@ function createSectionsEditor({style, onTitleChanged}) {
     updateLivePreview();
   });
 
+  updateHeader();
+  rerouteHotkeys(true);
+
   $('#to-mozilla').addEventListener('click', showMozillaFormat);
   $('#to-mozilla-help').addEventListener('click', showToMozillaHelp);
   $('#from-mozilla').addEventListener('click', () => showMozillaFormatImport());
@@ -47,17 +50,22 @@ function createSectionsEditor({style, onTitleChanged}) {
       .forEach(e => e.addEventListener('mousedown', toggleContextMenuDelete));
   }
 
-  let sectionOrder = '';
-  const initializing = new Promise(resolve => initSection({
-    sections: style.sections.slice(),
-    done:() => {
-      dirty.clear();
-      rerouteHotkeys(true);
-      resolve();
-      updateHeader();
-      sections.forEach(fitToContent);
+  const xo = window.IntersectionObserver && new IntersectionObserver(entries => {
+    for (const {isIntersecting, target} of entries) {
+      if (isIntersecting) {
+        target.CodeMirror.refresh();
+        xo.unobserve(target);
+      }
     }
-  }));
+  }, {rootMargin: '100%'});
+  const refreshOnView = (cm, force) =>
+    force || !xo ?
+      cm.refresh() :
+      xo.observe(cm.display.wrapper);
+
+  let sectionOrder = '';
+  let headerOffset; // in compact mode the header is at the top so it reduces the available height
+  const initializing = initSections(style.sections.slice());
 
   const livePreview = createLivePreview();
   livePreview.show(Boolean(style.id));
@@ -83,28 +91,26 @@ function createSectionsEditor({style, onTitleChanged}) {
   };
 
   function fitToContent(section) {
-    if (section.cm.isRefreshed) {
+    const {cm, cm: {display: {wrapper, sizer}}} = section;
+    if (cm.display.renderedView) {
       resize();
     } else {
-      section.cm.on('update', resize);
+      cm.on('update', resize);
     }
 
     function resize() {
-      let contentHeight = section.el.querySelector('.CodeMirror-sizer').offsetHeight;
-      if (contentHeight < section.cm.defaultTextHeight()) {
+      let contentHeight = sizer.offsetHeight;
+      if (contentHeight < cm.defaultTextHeight()) {
         return;
       }
-      contentHeight += 9; // border & resize grip
-      section.cm.off('update', resize);
-      const cmHeight = section.cm.getWrapperElement().offsetHeight;
-      const maxHeight = cmHeight + window.innerHeight - section.el.offsetHeight;
-      section.cm.setSize(null, Math.min(contentHeight, maxHeight));
-      if (sections.every(s => s.cm.isRefreshed)) {
-        fitToAvailableSpace();
+      if (headerOffset == null) {
+        headerOffset = wrapper.getBoundingClientRect().top;
       }
-      setTimeout(() => {
-        container.classList.add('section-editor-ready');
-      }, 50);
+      contentHeight += 9; // border & resize grip
+      cm.off('update', resize);
+      const cmHeight = wrapper.offsetHeight;
+      const maxHeight = (window.innerHeight - headerOffset) - (section.el.offsetHeight - cmHeight);
+      cm.setSize(null, Math.min(contentHeight, maxHeight));
     }
   }
 
@@ -367,7 +373,7 @@ function createSectionsEditor({style, onTitleChanged}) {
           if (replaceOldStyle) {
             return replaceSections(sections);
           }
-          return new Promise(resolve => initSection({sections, done: resolve, focusOn: false}));
+          return initSections(sections, {focusOn: false});
         })
         .then(() => {
           $('.dismiss').dispatchEvent(new Event('click'));
@@ -472,36 +478,33 @@ function createSectionsEditor({style, onTitleChanged}) {
     livePreview.update(getModel());
   }
 
-  function initSection({
-    sections: originalSections,
+  function initSections(originalSections, {
     total = originalSections.length,
     focusOn = 0,
-    done
-  }) {
-    container.classList.add('hidden');
-    chunk();
-
-    function chunk() {
-      if (!originalSections.length) {
-        setGlobalProgress();
-        if (focusOn !== false) {
-          setTimeout(() => sections[focusOn].cm.focus());
-        }
-        container.classList.remove('hidden');
-        for (const section of sections) {
-          section.cm.refreshOnView();
-        }
-        if (done) {
-          done();
-        }
-        return;
-      }
+  } = {}) {
+    let done;
+    return new Promise(resolve => {
+      done = resolve;
+      chunk(true);
+    });
+    function chunk(forceRefresh) {
       const t0 = performance.now();
       while (originalSections.length && performance.now() - t0 < 100) {
-        insertSectionAfter(originalSections.shift());
+        insertSectionAfter(originalSections.shift(), undefined, forceRefresh);
+        dirty.clear();
+        if (focusOn !== false && sections[focusOn]) {
+          sections[focusOn].cm.focus();
+          focusOn = false;
+        }
       }
       setGlobalProgress(total - originalSections.length, total);
-      setTimeout(chunk);
+      if (!originalSections.length) {
+        setGlobalProgress();
+        fitToAvailableSpace();
+        done();
+      } else {
+        setTimeout(chunk);
+      }
     }
   }
 
@@ -540,7 +543,7 @@ function createSectionsEditor({style, onTitleChanged}) {
     updateLivePreview();
   }
 
-  function insertSectionAfter(init, base) {
+  function insertSectionAfter(init, base, forceRefresh) {
     if (!init) {
       init = {code: '', urlPrefixes: ['http://example.com']};
     }
@@ -557,15 +560,18 @@ function createSectionsEditor({style, onTitleChanged}) {
       prevEditor,
       nextEditor
     });
-    if (base) {
-      const index = sections.indexOf(base);
-      sections.splice(index + 1, 0, section);
-      container.insertBefore(section.el, base.el.nextSibling);
-    } else {
-      sections.push(section);
-      container.appendChild(section.el);
+    const {cm} = section;
+    sections.splice(base ? sections.indexOf(base) + 1 : sections.length, 0, section);
+    container.insertBefore(section.el, base ? base.el.nextSibling : null);
+    refreshOnView(cm, forceRefresh);
+    if (!base || init.code) {
+      // Fit a) during startup or b) when the clone button is clicked on a section with some code
+      fitToContent(section);
+    }
+    if (base) {
+      cm.focus();
+      setTimeout(scrollToEditor, 0, cm);
     }
-    section.render();
     updateSectionOrder();
     section.onChange(updateLivePreview);
     updateLivePreview();
@@ -599,7 +605,7 @@ function createSectionsEditor({style, onTitleChanged}) {
     }
     sections.length = 0;
     container.textContent = '';
-    return new Promise(resolve => initSection({sections: originalSections, done: resolve}));
+    return initSections(originalSections);
   }
 
   function replaceStyle(newStyle, codeIsUpdated) {