Adding a variable to a sub-category by typing in “Cat|SubCat” works fine, but dragging a variable into that new subcategory would actually make a new category called “SubCat” and move it there. It’s a minor bug but still be nice if it worked as expected.
Thank you for your report. I was able to easily reproduce this issue in 4.3, so I have entered a report to our developers letting them know. If you encounter any other unexpected behavior, let us know.