No @QMcKay we don’t have Show Entity Screen action yet but I don’t know if I’ll be able to resist that 
Creating a Show Entity Screen is something complex. SambaPOS needs to know the reason of switching screens to be able to navigate correctly. For example coming back to ticket after Choose Customer > Edit Customer > Select Customer is something different than doing it while there is no ticket open.
For @Jesse’s case executing Change Ticket Entity action, setting entity type parameter to entity type and leaving entity name blank will switch to related custom screen. Also executing Display Ticket action with 0 parameter will come back to ticket. If we remove references from ticket type to custom screen entities we won’t see Select XXX buttons.
I hope that won’t disappoint you…