Can you confirm it’s not this (from the release notes):
Just to be clear, if you have a genre in your tags called Post Bop, and you want it to appear under Jazz, you should find it in under Uncategorized and set the parent genre to Jazz.
Alternatively, if you want albums with the file tag Post Bop to be grouped in with the existing Roon genre Post-Bop (our metadata providers use a dash), you can set that up under Settings > Setup > Genre Mappings.
Once the mapping is set, any albums that have the file tag Post Bop will show up as Post-Bop, even if the album is unidentified. This allows you to map your own genres to the hierarchy Roon uses out of the box.
Does that make sense? It’s extremely flexible, but it requires a little thought about how exactly you want to use genres in Roon.