You are so used to wielding a shield that you can do so even while using the hand that's holding it for other tasks that require the dexterity of a hand.
Archetype
Feat type
Archetype Feat
Level
6
Traits
Archetype
Prerequisites
Bastion Dedication
You are so used to wielding a shield that you can do so even while using the hand that's holding it for other tasks that require the dexterity of a hand. The hand you use to wield a shield counts as a free hand for the purposes of the Interact action. You can also hold another object in this hand (but you still can't use it to wield a weapon). This benefit doesn't apply to tower shields, which are still too cumbersome.
Source: Pathfinder Player Core 2, p. 187
Bring Nimble Shield Hand into a Pathfinder 2e game with The DM Screen.