I wish this was easier. I have a workflow that I use to create stacked PRs which involves changing the target branch of the next PR to `main` after merging its predecessor, but it is too fragile to institute as a policy.

However, this is also just a more specific version of the general problem that long-lived, elaborate topic branches are difficult to work with.

jj makes this mostly trivial - well worth checking out if you’d like to work this way, but GitHub gets in the way.

    git rebase --onto squashed nonsquashed next-pr

Works fine in my experience (except when submodules are involved)