Custom Item Sets Bug (Mac OS)

For some reason the custom item set on Mac dosen't work, you can create an empty item set but you cant drag and drop any item to it, no matter what I do, it won't work. I haven't experienced anything like it on the Windows, but it won't work on Mac OS. It's not a big problem, I can still fix the item set on Windows and then Mac will save the item set from Windows(I'm playing on both Windows and Mac using the same account), but it's still annoying to change the item set on Windows when I can just change it when I'm playing on Mac. I don't know if there's other Mac players experiencing the same problem or is it just me? Either way, anyone know how to fix it?