Earlier quoted context omitted.
use an open source password manager that supports them. as others mentioned, there's BitWarden (cross-platform, self-hostable), but if you want something simple there's KeePassXC (and you can put the store file on a dropbox shared folder)
I resent that I need a special app to "manage" them. I want to know where this key is on my filesystem so I can back it up and edit it myself, not have to use some app to access it. My ssh authorized_keys is just a text file. I can "manage" it with something as simple as vim. Maybe KeePassXC and BitWarden give you that simplicity, if so great!
[1] https://github.com/keepassxreboot/keepassxc/issues/10407#iss...