OK I'll admit I didn't realize you could right click -> "customize toolbar". That seems to work in almost all native apps (Mail and Finder for me, at least). And you can turn on text labels in the options!

Finally I can get rid of the tagging button in Finder and replace it with a New Folder button. And I can ditch all of those buttons I don't use at the top of the Mail app to keep the "search" bar open at all times.