Wow. I was using 'Tab Mix - Rename Tab' before, but Tab ReTitle is far better.

Unlike 'Tab Mix - Rename Tab', I can assign a tab title to any URL. So that means I can open a new tab to that URL and it gets my custom title. I can also go to that URL within a tab and it gets my custom title. I can go Back or Forward to that URL within a tab and it gets my custom title. It's also persistent across sessions. So this completely solves the problem for me of how the YouTube history page just gets titled, "YouTube" instead of "History - YouTube".

Unlike 'Tab Mix - Rename Tab', the titles of YouTube videos aren't always automatically renamed to just 'YouTube". With 'Tab ReTitle', the video titles show as expected without me having to change any settings. It just stays out of Firefox's way (unlike 'Tab Mix - Rename Tab')!

There are a few other instances where the title never showed the way I wanted it to show, and 'Tab Mix - Rename Tab' couldn't help because it was just for that tab only and if I closed it, that was it, it was gone. Going to other pages in that tab meant the title doesn't change because I had simply renamed that tab. With Tab ReTitle, everything is exactly as it should be.