Genres
Genres are handled differently than Subjects. Genres are not editable; they are "hard-wired" into the code because certain values (eg, Fiction) are tied to elements in the ONIX standard (and other wholesaler templates). So, if you would like to create/update/delete genres, you'll need to submit a request to TitleLeaf support. Aside: Assigning genres to products, on the other hand, is nevertheless under your team's control like any other data point
As cited in the ingestion templates, acceptable genre values during ingestion are:
Beginning reader
Chapter book
Fiction
Graphic novel
Hi-lo
Leveled reader
Narrative
Nonfiction
Picture book
Young adult
The labels for these genres can be overridden on the public site. Again, you'll need to submit a request to TitleLeaf support.