Ctrl+d bookmarks the current tab. Not sure if there are bookmarks for selected tabs but you could see what happens if you hit that while you have more than one tab selected.

After looking over some of your posts on these Firefox communities, I believe you're well into "time to make my own addon" territory.

I've written a single addon myself, and while I found documentation to be lacking, it isn't as hard as it first feels. What really helped is finding other plugins on GitHub that did something somewhat related to what I was attempting, which gives you a solid base.