I've added a "show sync indicator" setting to v1.4.0 of the Extra Markdown editor settings plugin.
It can be set to:
- "With text": Adds a text panel to the top of the editor that shows the sync status:
- "With an icon": Shows an icon that indicates the sync status. The "edit" icon means that the note has been edited 1) since opening the editor and 2) after the start of the most recent sync:
Note: If the plugin is loaded by Joplin during a sync, it may incorrectly report the state as "[Not syncing]" until that sync finishes.