Changing which program responds to media keys

When I start a VLC instance, I can control it with media keys (Fn, BT headphones, etc.). But if I then start a second VLC instance simultaneously, I cannot control that one with media keys. That's probably intended, it would usually be pretty annoying if both reacted. But if I then close the first VLC instance, nothing reacts to media keys. And sometimes I simply want to decide that from now on, media keys should control a different program. PulseAudio has so crazy many features, surely I can somehow switch my media keys over to another program or instance, right? How do I do this? (Having a command line method for scripting would be nice as well.) Setup info, in case it's relevant: Manjaro 21.1.2 KDE 5.22.5 PulseAudio 15.0 VLC has some buttons bound, but most are set via KDE's system settings or just left default. Both have the exact same issue.