Is there a keyboard shortcut to bookmark a post? And if there isn't, could we add one?

I bookmark posts very frequently (on Stack Exchange, not in my browser), enough so that I would really appreciate a keyboard shortcut to be able to do that. I have looked all through the options in Shift+?, and there doesn't seem to be a shortcut.

There are shortcuts to vote, to see the timeline of a post; could we add one more keyboard shortcut in that area?