When attempting to Categorize a mod, I need to move my focus into the Category field first before I can start typing.
Normally, clicking anywhere inside the field moves my focus to that field. Eg clicking on the bullet-point-like symbol on the left side, or clicking in empty space on the right side of the field.
However if I try to click on the literal word "Category" that's in that field, my focus doesn't move into the field. I cannot type anything.
My computer tries to select the text of the word "Category" instead, which I can see because if I double-click, it highlights the whole word.