I think that there may be a bug with selecting modes.
When I set it up with default settings in a subcategory, I only get the Option of ‘tags’. In order to access the assignment mode, I have to force it to be the default for the category. As I want to be able to easily switch between the two, it would be nice to have this working as displayed in the video in the OP.
@david, would you mind taking a look?