I'm bumping this conversation, since the pull request from @personalizedrefriger was closed with no resolution and I'm not sure my replies on closed PR have any visibility.
As @laurent wrote:
Do you have examples of applications doing this? It feels a bit like clutter on the UI and many people won't know what these icons mean. Or perhaps the solution is just to trigger a sync very shortly after a note has been changed (now I think it's a few seconds), in which case such icons become less necessary.
As I replied on Github, unless you can guarantee that the last word I typed will be pushed to the server, even if I minimize the app by pressing the Home button on my iPhone, we need to show sync status. As a user, it's super important for me to know that my work has been saved and synced. It's not "clutter" to display such important information!
I then posted a few examples from other apps: Mobile: Add sync status icon by personalizedrefrigerator · Pull Request #6785 · laurent22/joplin · GitHub
I can share many more if needed.
I found this old forum thread for a similar feature request: Display sync status in titlebar
@tbergeron made a plugin at the time but it looks abandoned? (no update since 2020)
At the very least, Joplin could display the sync icon only while the sync is ongoing (or had errors), then hide it when the note is fully synced. That would be one way of reducing clutter if we think it's that problematic (which I don't think it is)