Controlling something else that's on

A Remote Design can target any number of devices so the second paragraph of your message is not actually the case.

The general solution to what you’re asking however is either to enable ‘Show Manual Remote’ for that device so that you can quickly popup a remote for diagnostic purposes, or create an Activity specifically for that other device that doesn’t change inputs for instance.

Ah, I see what that does now (Show Manual Remote). I thought that would enable a popup at the bottom of the remote that DOES show up; but instead it adds it in another section at the bottom of my Activities page.