profile update

Log into Manage your Apple ID using for Apple ID and Password. It should list all devices associated with that Apple ID

You cannot manually; it is now done automatically when using one you are signed into iCloud/Apple ID with.

It still does not have an option to add a device manually - only remove it.

Thank you though the OP only asked about manage devices. That could be as you mentioned to add or could be to remove or still only to inventory

How ever think all angles are covered ☺️

How ever think all angles are covered

that's always good!