Add Subrole - Missing command

Has anyone experienced and issue where the Add Subrole button will not show up in the Edit Roles panel? I can't get it to show up, no matter where I hover over the place it is supposed to be, so I'm limited to only the subroles created automatically by FCP. I've searched google extensively and have not found any mention of this problem. It's probably something I'm doing wrong. Thanks!

2015iMac, OSX 11.0.1, recently updated to FCP 10.5.2 to see if that fixed the problem but it did not.

There's no button down at the bottom.

Start by resetting your' preferences. 

Hover over a role and you should see it.

Thanks Ben, but that is exactly what I'm doing. I've done it many times before, only now, the + Subrole icon simply does not show up. Just empty space where it should be. I've tried different libraries etc. 

As mentioned previously, hold Cmd+Opt while launching FCP, delete preferences. Try again.

Thank you Tom and Ben, that worked!! I've been using FCP X everyday since it was released and I think that's the first time I've had to trash preferences. I remember doing it often with FCP 7. I had forgotten all about it.