If you are still trying to accomplish your Add (as Next to Play) command idea, I'd suggest waiting. There's been progress. It is still Beta though, I believe (unless he made it public recently, I've been busy this week), so I've been waiting for it to become public before I said anything.
EDIT: Looks like Matt outed it himself in your other thread. I've tested it briefly. It works as it says on the tin.
You're right. It is related to my Control-Panel-Project.
I am happy to wait a little longer if progress can be expected here.
Are you involved as a member of the beta team?
A few more suggestions:
MCC commands should work as independently of the context as possible. It would therefore only be logical if commands like MCC_LIST_SEND_TO_PLAYING_NOW would work in every view.
The commands in the context menu of the TheaterView are, for example, Add, Add Artist, Add Album. The latter is unclear if the selection is on an artist. And that doesn't make any sense in views with photos. The 'more play options' menu shows 20 entries. I have to scroll to read them all.
Instead, a general treatment should be sought:
It is sufficient to distinguish whether the focused element or the filtered selection is added. And each of the two commands with the option 'Replace the title in Playing now', 'Insert next' or 'Append at end'.
This general approach would work with every view and structure. No matter if you categorize file type, genre, actor or watever.