U_USER default selection screen not loading

[#1]

hello all

I extensively searched in the many answers addressing selection screens but did not find a solution for this (I think simple) issue.

I created U_USERID selection screen for standard transactions such as ME2M, MB52 etc. but when I start the transaction, the selection screen for this variant is not defaulted.

Is there an activation or some limitations I am not aware of for this variant? the user id consist of 6 Char.

thank you for a reply

[JL23]

To my knowledge does this U_USER variants only work in plant maintenance transactions.