Plexamp/safari/play(watch later app) media player support

I’d love to be able to control Plexamp (self hosted music service, part of Plex) and safari YouTube videos ( Play is amazing for watch later vids and saved music

https://apps.apple.com/us/app/play-save-videos-watch-later/id1596506190)

that are playing in the background with dockside controls. If I add them through custom media app settings in dockside, can’t control anything as I assume special integration is required?

I’ll understand if this all is too much of a hassle to code :D