Click the trash icon in the upper right of the lineup. It's removed from the pool.
If you want to remove many at once, use a lineup filter instead. A filter on a group or on the Lineup Pool removes any lineup that doesn't meet a threshold you set, such as a minimum Saber Score or a maximum ownership, and the diversifier works only from what passes. If the lineups you don't want share a player or a stack, uncheck that player or stack, apply, and SaberSim rebuilds around your request.
