So assuming that condor_store_cred really wants to talk to the schedd
It should be talking to the credd. (Command 479 is STORE_CRED and listed as a schedd command, but that's only for Windows, which had the command first.) The tool was never updated, I guess, to reflect that it's talking to the credd when dealing with OAuth2 credentials.
The credd's Name (the specific ClassAd attribute) defaults to the FQDN, which is why it looks like `-n` requires one. Running `condor_status -af MyType Name` should show you (look for `CredD`) what to pass to `-n`.
-- ToddM