New service GUI and relational fields

Hello

In the old service we were able to manipulate what could and would be shown in the ticket fields i.e edit ticket screen. 

Lets say we have a field on ticket from an entity (sale/project/appointment or another table) and in the dropdown/search field I only want to list only those projects that have status != closed and are connected through erp.  

What approach does our fellow community developers have to solve issues like this ?