Movement Modifiers for Prototypes and/or Decks/Cards

I’m currently in the middle of creating a new modified version of Elder Sign with a gameboard and new movement rules.

I’ve been trying my best, but I cannot find the proper Trait for an Item that binds an entity to only being able to be selected by holding Shift.

Could someone help me with this?

Thank you.

It is found in the Does Not Stack trait