I use Firefox when surfing the web, or YouTube, to gather ideas and put similar themes into existing open windows. I then go back to these later to see which ones I wanna keep and delete the rest. I'd like to see a bit more tab management to help with that. I might have 10 different Windows open in Firefox at any given session, each with 10 - 20 tabs in them.
I don't know why this doesn't already exist, but when I right-click a selected tab at the top of the window, I'd like to see a new feature: Move to Window, which then brings up a list of available open Windows for me to choose and select one, after which that tab is moved to others in that Window. Can that be done? Awesome if you made Firefox even more betterer!