Hi, 

There are 2 options: 

1- add a domain pointing at picking_type_code == "internal" And picking_type_id.sequence_code == 'PICK'

2- Add compute field, is_pick for example, which will be True if conditions writtten in 1 are OK or you can even check the locations of the picking_type_id: if movement is from A to B , then you consider it a PICK operation => ('default_location_src_id', '=', REF TO A), ('default_location_dest_id', '=', REF TO B)

if your process is normal pick pack ship, i would recommand option 1. it's simpler and faster.

But if you work on multi company or you have different pick locations with code that can change.. i'd recommand option 2.

hope this helps.