darktable 3.8.1 on MacOS module preferences problem

Hi- I’m helping a young man in Mexico set up darktable 3.8.1 on a very new iMac. I’m not sure of the model and OS version, and can get that on my next visit.

I was trying to create a new module favorites group for him, and I can’t seem to get the pop-up list to show by pressing the + box. It seems to have shown up only once, as I did add a module, but I can’t get the popup list to show again. I suspect it is opening, but behind a window somewhere.

I run dt myself on a linux machine, not having a problem like this, and I’m not too familiar with MacOS these days.

Any help would be gratefully received. Thanks.