Not So Feudal System

The Claim Throne scheme lives behind the Meritocracy perk (Stewardship lifestyle), targets your liege's primary title and runs on Learning. The wiki build: replace any duke-tier vassal with a custom ruler - Midas Touched education, Impatient and Schemer, points into Stewardship - take the Domain focus and spend the free perk on Meritocracy, then scheme away. You only need the scheme to SUCCEED (a pressed claim lands in your lap); pressing it is optional. NB the scheme route does not count for Upward Mobility - that one wants the diplomatic interaction instead.