It should be possible to set the sorting of the user option entry list.
We have a catalog item/offering with an user option which is linking to another table.
If I want to order this item I will get a list of entries for this user option which is OOTB sorted by ID, logical name or similar.
In Service Manager itself and in the ESS Client it is possible to change this sorting e.g to the field DisplayLabel.
But this changes do not have an effect to the SMA SM Portal and also in the SMAX there is no way to change the sorting.