Lay out the publishing forms in one column on phones.

Below 600px: labels above full-width inputs, 44px touch targets, 16px
text, and the tabs on the top border of the story box.

publish/editor.css

@@ -290,3 +290,101 @@
   margin-top: 10px;
   font-size: 10.5pt;
 }
+
+/*
+ * Phones: the editor takes the full width and grows only downwards, the
+ * toolbar buttons are big enough for fingers (the toolbar wraps onto a
+ * second line), and the text is at least 16px so that iOS does not zoom.
+ */
+@media (max-width: 600px) {
+  .xed {
+    max-width: none;
+    min-width: 0;
+    resize: vertical;
+  }
+  /* A wrapped line would start with a separator, so the groups have
+     space between them instead */
+  .xed-toolbar {
+    column-gap: 8px;
+  }
+  .xed-group + .xed-group {
+    margin-left: 0;
+    padding-left: 0;
+    border-left: 0;
+  }
+  .xed-btn {
+    width: 40px;
+    height: 40px;
+  }
+  .xed-btn svg {
+    width: 18px;
+    height: 18px;
+  }
+  .xed .xed-source {
+    font-size: 16px;
+  }
+
+  /* Dialogs: labels above the inputs, and bigger buttons */
+  /* Only the body scrolls, so the title and the buttons stay in view */
+  .xed-window {
+    display: flex;
+    flex-direction: column;
+    width: calc(100vw - 20px);
+    overflow: hidden;
+  }
+  .xed-window-body {
+    min-height: 0;
+    overflow: auto;
+    padding: 14px;
+  }
+  .xed-form {
+    width: auto;
+  }
+  .xed-row {
+    flex-direction: column;
+    align-items: stretch;
+    gap: 4px;
+  }
+  .xed-row label {
+    flex: none;
+  }
+  .xed-textbox {
+    flex: none;
+    height: 44px;
+    font-size: 16px;
+  }
+  .xed-button {
+    min-height: 44px;
+    font-size: 16px;
+  }
+  .xed-close {
+    width: 44px;
+    height: 44px;
+  }
+
+  /* The special characters wrap in a grid of cells big enough to tap;
+     a touch screen has no hover, so the preview is left out */
+  .xed-charmap-body {
+    display: block;
+  }
+  .xed-charmap {
+    display: grid;
+    grid-template-columns: repeat(auto-fill, minmax(40px, 1fr));
+    width: 100%;
+  }
+  .xed-charmap tbody,
+  .xed-charmap tr {
+    display: contents;
+  }
+  .xed-charmap td {
+    display: flex;
+    align-items: center;
+    justify-content: center;
+    height: 40px;
+    min-width: 0;
+    font-size: 20px;
+  }
+  .xed-charmap-preview {
+    display: none;
+  }
+}