How to estimate takeoff shift(A320)?
 

Accordingly to our SOP we should enter the takeoff shift distance if takeoff is to be from an intersection. If a runway has a displaced threshold but we take off from the beginning of the runway (LEBL 07L) what distance should we enter as takeoff shift: nothing or distance between the beginning of the runway and displaced runway threshold??
Takeoff shift value must be positive but what should we use as reference point? a displaced runway threshold or the beginning of the runway?

You'd do it to the runway threshold in the database, as that's what the FM position updates to at TO.

But do your SOPS make you do it if you have GPS PRIMARY?

If you have GPS then don't bother.