It would be nice to get some kind of official confirmation that the ability to add custom CSS isn't going to go away, given that the justification for dropping

It would be nice to get some kind of official confirmation that the ability to add custom CSS isn't going to go away, given that the justification for dropping compact mode seems to basically boil down to it being hard to discover, and Mozilla assuming (without user metrics) that nobody uses it. How much harder is it to discover the ability to write custom CSS? Do we know that Firefox won't apply the same logic to that feature?