Mascot added the ability for users to add a custom eBay category to each item listed via Mascot. To do this, select item(s) to list for sale ---> Sell Selected ---> check off eBay ---> under "Items to List", see the column titled "eBay Category" --> select the drop-down and choose which one of your custom categories you want the item to go into! Once complete, simply select "Confirm Bulk Listing".
Note: eBay Custom Category on Mascot will pull in whatever custom categories a user has in their linked eBay account. To add additional custom categories, visit your eBay Seller Hub --->Store --->Store Categories.