How to sort tracks by Tracknumber, not by Title?

[Gijs Schubert]

Gents,
I'm using MS on Synology NAS to operate a Naim system. On the Naim app I make all kind of selections (on artist, genre, album etc), and once I display the individual tracks, I have opted to display not only the (track)title but also the tracknumber with a dot before the title and the album after the title separated by a /. I have done that as follows (and it works perfectly fine):

Tab Server: itemTags = Tracknumber
Tab Advanced: tagFormat = Title.displayFormat={$tracknumber^^. ^$title^^ / ^^$album}

The issue is that the sort order of the selected tracks is (still) displayed by (track)title, not by tracknumber.

How can MS sort my selections by tracknumber, not by title? I have tried all kind of strings in tagOptions but only red response....