Hi,
I cannot add categories to the field in the image. Categories are not correct. In April 2018, this problem was experienced by someone else. You said you’d be solved by the next update. I hope you solved it 🙂
This drop down shows all the existing categories. If you have more categories than shown in the dropdown, deactivate all the plugins not related to the theme, and switch to the parent them if you are running the child one and provide your site admin access to the private area.