I thought I have seen a way to send a status request other than from button on main screen. Is there a action item anywhere to send status requests? I cannot find. Maybe I was dreaming.

Choose the Control Light / Appliance Type in the Action panel then a Send Status Request Action should be available in the next popup.

Boy do I feel dumb. I looked there but didn't see. Sorry to waste your time.

Only insteon devices were listed. Any way to do same thing with a plugin device?

Only if the plugin device supports some kind of command to do it. If they implement dimmer or relay device types, then the plugin will get a message to do the status request when you select the UI mentioned above so if they handle that message it should work. Custom devices though will have to expose a custom action to update status.