DRAG DROP A company has the following custom permission set: 
Change Assignable to true, publish the app, then add Permission Sets page permission. You need Assignable set before anything else or it won't show up, and publishing registers it in the environment. The last step (adding page permission) is needed so users can actually access/manage the set. ObsoleteState and IncludedPermissionSets are common distractors here, so don't get tripped up! Pretty sure this is what Microsoft expects but let me know if anyone sees it differently.
