Default Upload Location for asset fields on a User...? when setting a Default Upload Location for a field that’s attached to a User, what’s the variable to use that would ensure the file is uploaded to the User I’m editing’s account in the back end, and not my admin user account - which is what {{currentUser.username}} does?

I haven't been able to find out and everything I've tried hasn't worked. e.g., Could not resolve the subpath “{user.username}”. And {{ user.username }} uploads to a folder for my admin account.
Assuming you want the folders to be named after the users' IDs (since they won't change), the subpath should be {id}.