Another example is `jj rebase -d main`. It may look very similar to `git rebase main`, but it rebases a whole tree. See https://stackoverflow.com/questions/17315285/rebasing-a-tree... if you don't know what I mean.

Another example is `jj squash --from main..my-branch --into my-other-branch some/path`, which removes all the changes to `some/path` that happen in any commits in `main..my-branch` and squashes them into the tip commit of `my-other-branch`.

Does that help? I'm not sure I understood your comment correctly.