When looking at devices it is nice to type in a filter to find things. It would be nice if we could get a filter when we are in RM and selecting devices - if I could filter on "plug" I'd know I found them all without scrolling through 300 devices and reading them.
I agree. Would be a nice addition.
I now it's not RM, but with webCoRE you can type in a box above the device drop down. For me 'Kitchen' would bring up all my kitchen devices. You get the idea.
Your browser's built-in search feature might help here. Ctrl+F (or Cmd+F) should work, though I'm a fan of Firefox's (other browsers might have this too) slash-key shortcut for the same feature. This won't look through just the list, but if you have a substring of the device name(s) in mind, it's usually close enough.
But yeah, something like you suggest would be quite good, or perhaps putting Rooms to greater use and allowing filtering or searching based on those, too. This is my workaround in the meantime.
What also would be nice is if devices already used in the rule appear at the top of the list.
It would be great if in RM, when you are selecting the device, there is filtering textbox same as when you are selecting room on device details page. And also if devices in this RM list could be grouped by room. Something like this: