Stacking commits lets you do that without having to wait for each change to be reviewed/merged to the main branch before you iterate on top of those changes.
It's such a complicated way to work though, you start another set of changes then you go back addressing comments then you go back updating the stacked branch and you might need to do that few times... Teams should focus on getting stuff merged in and not create massive PRs that live forever, life becomes so much easier.
True. I find I rarely need it: standard rebase or merge do the trick. If they don't the review cycle or PR size may be too high. Super rare I need onto. So rare I look up how to do it when I do.