This proves difficult as I do not know how to work the new create hub pages; I find the UI complicated and not easily navigable. Worse, it seems you can’t actually fetch the assets of banned accounts. I remember you could always do that when the old “Create” page was still around.
You’re not able to look through any assets that belong to them. The toolbox would think the player doesn’t exist.
I’m not sure if there’s an endpoint that returns the owned assets of a given player, since that would be pretty intrusive! I doubt an endpoint like that even exists.