Yes, it is a User field. We’re getting tripped up by some confusing terminology. I said “Relational” because the User field type is one of several fields (Page Link, Post Object, Relationship, Taxonomy, User) listed under the “Relational” category. I hope that clarifies things.
There’s really no code to show you for this. So far, it’s all in the GUI. The select field is being used when the user is creating or editing a custom post type. The choices (users listed as editors) are being populated automatically because it’s a relational field.
Is there something I can add to functions.php or someplace to set the default value for the editor field to the current user?
The latter. This is a post for recording some basic information for projects users will be managing. This info includes the name of the project manager. Often (but not always), it will be the current user, so I’d like that user’s name selected by default.