Stash Git changes, but keep staged changes

Today I had been working on a branch, and wanted to separate out one set of changes into a separate branch. To do this, I staged the changes I wanted to separate out, and then ran

$ git stash --keep-index

This stashes all entries, but keeps the staged code. This meant I could do

$ git checkout main
$ git checkout other-branch
$ git add ...
$ git commit ...
$ git checkout previous-branch

and then resume work on previous-branch.!