my worry is that by firefox 225 that option will be gone, or will require modifying some text file in your profile.

I say this because I already have had to modify a text file in my profile to get firefox to do what I want (tree style tabs without dupe tab-bar on top).

also, by "firefox 225" I wonder how easy it will be to arbitrarily modify a 'protected' app/system text file (this is already difficult on smartphones)