As far as I explored my new M+, I am not able to search user samples by typing filename.
(And not talking about two-levels user sample subfolders, that's another shamie topic:))
I am the kind of a person with a larger sample library portfolio, including my own designs and recordings. I understand that you wish to push your own expansions to the face of user spotlight, BUT... :)
Anyway I like the M+ mashine very much, it feels very simple, fast and effective.
Love, Lukas