Is there a way to do that today?

For updating bookmarks I've found like half a dozen variants of `tug` alias the community has come to using which is just a slight improvement (bit daunting to newcomer to pick 'best' one and not fan setting up aliases on all my working devices).

It would be nice if jj was better than git for the fundamental workflows like this out of the box overall.

Yes, it's called "experimental-advance-branches" (because it landed before the branch -> bookmark rename). Here's an example of setting it:

https://github.com/jj-vcs/jj/blob/c70f9b5b3fff08a86fb11afc57...