Cursor position should be restored after returning to editing from preview

### What
User edits the note and switches with `Cmd+Shift+P` (or button) frequently to check preview and then goes back. Every time the user goes back, the cursor is not placed anywhere ~> it would be much better if the cursor stayed at the previous place by itself.

### Why
1. Better UX
2. This is so in Electron

Start by tracing the Cmd+Shift+P and preview-toggle behavior in the macOS editor. Identify where the editing cursor position is lost when returning from preview, then verify that switching back restores the previous position through both the shortcut and button paths.

Written by the indexing model from the issue text.