Huh, I thought I had put it in SwiftUI. In any case, the answer turns out to be a bit of a hack (IMHO): you have to call NSApp.sendAction from the Command, and send the action to nil, which sends it up the NSResponder chain. No way I can find to target a specific instance, but that’s not too much of an issue for me. What doesn’t seem to work is the enabling/disabling of menu commands.