You’re working on a series of PRs, one per branch, each one based upon the precediung one.
trunk -> my-feature-1 -> my-feature-2 -> my-feature-3 -> my-feature-4
Then you get a code review on my-feature-1 and you need to make a change. Now you need all the branches from my-feature-2 onwards to be rebased on the new my-feature-1 and for that to be reflected in your local.
$ git switch my-feature-4 $ git rebase --update-refs my-feature-1
--update-refs will save you having to go to each branch in turn and rebase.
Here’s an example git repo.