So when I click the (+) button, the element isn’t being added to my active soundset.
Heya, just a quick response while I am out that MAAAAY help. 
Is the SoundSet you are trying to add to YOURS to edit? Do you need to Duplicate it first?
it is a custom set I made, and it works sometimes. Like any element with the Musical note Icon appear to be added when I push the (+) button, but any element that has a different icon isn’t added
I’m still having this issue. Any suggestions?