same. saved my ass already a few times when doing some reverseengineering voodoo. being able to set a valid https cert makes it easier to redirect apps than to bypass forced HTTPS. had to pretend to be a update server for something once and patching the URL was enough via getting a cert quickly (using DNS-01 challenge, no exposed ports ever)

you can use a secondary firefox profile. starting firefox with the --no-remote -p switches allows to load it alongside the main profile (-p loads the profile manager and --no-remote suppresses the "open new window in existing profile" behavior