I’m not sure there is one. But the underlying dashboard app either subscribes to a device’s events, or it doesn’t.
So if one has no plan to use a device on the dashboard, it’s best not to include the device in the dashboard app’s settings page.
It would be nice if there were a one-step method to both include the device in the dashboard app’s subscriptions, and add it to the dashboard display itself.
But in my limited understand of how all this stuff works (confirmed somewhat by @thebearmay’s explanation above), that’s not how it was designed. Perhaps it’s not possible for it to function that way without a more fundamental rewrite of how the platform and the dashboard app works.