Rebase onto commit

This is such a common operation that I kind of assume that there is some hidden key for it, but how do I rebase onto a commit? Only option I find is to rebase onto a branch's HEAD which is rarely something you'd want to do in a larger project.

In case that is not implemented I highly suggest doing that.

**Describe the solution you'd like**
When in commit section press r to rebase onto commit. Well, r = rename, so probably another key - you get what I mean.

**Describe alternatives you've considered**
Using maggit or raw git commands. Ugh.