You may be on a different version of Firefox as I don't recall any major changes to the Bookmarks workings over the past months or so.
To create a Bookmark from your current tab, hit Ctrl-D. See if that works and restores a semblance of normality. It may not of course. There is a 'Manage Bookmarks' window that you can also access by hitting Ctrl-Shift-O. Once in that window, I think you can click on any bookmark and you will see the properties of it at bottom right. Edit these at will.
I can find all of these by using the 'hamburger' menu that is at rop right of my Firefox window (the three horizontal lines that somewhat resemble the structure of a hamburger). Open that and click on Bookmarks in there.
All of this based on Firefox on a Win11 machine. If you are on a different OS or older Windows version, it may all look different.