I keep those kind of numbers in Keepassxc and cut and paste them when I need them. It's not that I don't trust FF I just think having one storage place is better than having two and it's just not necessary for FF to have them. A few extra seconds of copy pasting inconvenience is a price I'm happy to pay. For extra security I never cut and paste the CVC, that's always manual entry from memory.
I keep those kind of numbers in Keepassxc and cut and paste them when I need them. It's not that I don't trust FF I just think having one storage place is better than having two and it's just not necessary for FF to have them. A few extra seconds of copy pasting inconvenience is a price I'm happy to pay. For extra security I never cut and paste the CVC, that's always manual entry from memory.