It’s not possible to edit the default expense categories. However, you can delete any of the default expense categories that you don’t need by:
In the mobile app tapping the 3 dots in the top left corner or in the web app clicking the gear icon in the top right corner
Selecting Business Categories
Tapping on the category you want to delete
Tapping the Delete Expense Category button at the bottom
You can also create your own custom categories by following the steps here.