I think it’s not possible at the moment. It was suggested before here and even the co-founder made some comments about this feature, but it’s been over a year and a half with no updates on that.
This is something I’d love to see in Plexamp. For me Plexamp is missing only 2 features and this is one of them. Tbh they app is improving in a lot of aspects with every release so fingers crossed we’ll have this one soon.