Not sure why you don't have a scrollbar. On my version of Firefox (Firefox Developer Edition 67-0b16) the certificate list does have a scroll bar and can be navigated using the mousewheel. Can't speak for stable Firefox since I don't use that version.

No, not that I am aware of. In my own experience it actually took me longer to find alternative ways of bringing awareness to a bug I was having than it did to signup to Bugzilla and report it there.