Priming

A creature can learn an infinite number of Trained Skills. However, a creature's mind can only keep a certain number of skills at the forefront. Even the mage requires refreshers on old spells, or a martial artist on the fundamentals. Whenever a creature takes the Prime action, they can unprime any number of Trained Skills and Prime one Trained Skill of their Choice. Their Mental Capacity usage is then updated to the total of the Tier of the Trained skill that are Primed