Helium comes with support for genre styles and genres.
Genre styles can be used for defining which style a specific genre contains, similar to how Discogs implements this.
A genre style can for example be Electronic and the genres Techno, Ambient and Trance is mapped (connected) to this genre style.
When genre styles are used, they will be presented as top-level items in the Genres view with the connected genres as childs in the list.
Genre style blocks can easily be expanded/collapsed.
Working with Genre styles and genres
Start the Manage genres tool from File > Manage > Manage genres...
Click New style... to create a new genre style
When you select a genre style from the left list, all the connected genres will be shown in the right list.
If you would like to move an uncategorized genre, shown in the [Uncategorized] genre style, select it from the right list and click the Move to style... button.
In the dialog that shows up, select the genre style you would like to connect the genre to from the drop-down.
The results will be applied to the genres view the next time it is opened.