There already is a backup code on the site, so the sync could be done from there. If @Tryum idea is implemented, the IDE would always be up-to-date, and hence work from different computers (not at the same time) would be possible, am I wrong?
@SaiksyApo: Bellow ON/OFF button, I would add the text "Options ▼", that would allowed the user to parametrise the add-on. @Tryum idea would then be an option.
By the way, about his idea and the "CodinGame in read-only", I mainly code in an external IDE, but still use CodinGame IDE for quick debug. My utilisation would need both his idea both sync and disabling read-only.
You say @tryum idea consumes more ressources, I may miss something but I feel that the following is enough and doesn't consume much ressources:
1. Check updates of the file when tab get the focus
2. Update the file when the tab lose the focus and when modifications has been done in CodinGame IDE
Also, just a thought I have: During the The Great Escape, I'd have loved a toolbar containing both this plugin and the information that were in @grmel89 android app. Though related, it's a different project, but it might give ideas.