Rated 4 out of 5 stars
Excellent tool but it would be better if you could set "Embed favicon data in JSON Bookmark backup file" without it showing a progress dialog. There's really no good reason to be showing a progress dialog for an automatically-triggered background task like bookmark backups which aren't part of a Firefox shutdown.
(I can see the utility of having it when Firefox is doing a pre-shutdown backup, but I'm not willing to put up with it popping up and distracting me while I'm just working away normally. Better to not have it at all, even if that means having to back up my custom favicons by hand.)
The fact is... at the first, there is no progress meter. But when you have a lot of bookmark and slow CPU, it will take a long time and Firefox warn the user that my script may be error or hang, blar...blar...blar... Should Firefox terminate it or not? So, I need something to show the user that it is not hang, user should choose to continue to run it.
For the pre-shutdown backup, my script is also run but the progress meter is not show. (Ah-ha... you may not know that it is running nearly every time your shutdown Firefox !!!) I hide the progress meter during pre-shutdown because it is not necessary (YES - same as your reason).