If the category is within a metadata csv on import and is brand new, it will get added to the system (along with the tags inside). However if you can to create a brand new tag category, you can do it manually from within the admin.
To create a category…
There are a number of settings per category based on the collection type the tag is attached to or being view by per page, based on Tracks, Releases and Playlists…
Limit - the amount of tags that will appear on the page of the collection type (sorted by the most used tags on the collection type)
Order - the order in which the category appears in the tag category list on the collection page (zero being first in order), it is recommended to use spaces of ‘10’ to add the order number, so if you need to add a new category between two already ordered categories, you have the availability to do so.
e.g. You have the three categories, Genre, Music for and Instrumentation , you want Genre first, so it has an order of ‘0’, Music for second so it has an order of ‘10’ and instrumentation third so it has an order of ‘20’. You then want to change the order so Instrumentation is second. Since you have a gap of numbers based on the 10s order, you can just change the order number of instrumentation to ‘5’, making it second in order.
Single select - select this tick box if you would like to have the option of only ever filters via one tag within this category (no multiple filtering within the same category)
Visible - unselect this if you would like to hide the track