In the tab Widget Categories, you get an overview of all categories. For each selected category, the number of assigned widgets and widget groups are listed on the right.
On the right side, you can create a new category, delete a category and take a look at the description or which widgets are assigned to the category.
Click on the + on the right side to create a new category.
The category needs to be assigned on the list of widget or widget group itself, not in the overview of the widgets.
