So in your workflow you never "git commit -a"? So you have to always manually mark what you stage. Which is probably more work than always manually removing the changes you don't want to commit.

The ability to rewrite older commits easily in jj also looks like it would help with this usecase if you get it wrong once.

Concretely I think you would do is: Instead of staging part of your changes and then committing as in git, you would call jj split and split the commit into the part you want to keep local and the part you want to push. This way the local changes always stay in your working copy commit.

Even better, just commit the local changes once when you start. Work locally and before you push you call jj diffedit on your initial commit of the local changes and remove them. Now all the work you did since then will be automatically rebased on the edited initial commit and you can now push up. Instead of excluding your local edits every single time you just have to do it once before pushing.