I’m That works to a degree, but doesn’t solve the puzzle entirely. The place where it falters is: House Off and Nightlight On (in which I would need to nest Dining Room off) do different forms of “lights off” in the dining room (and other rooms).
House Off turns off all but one of the dining room bulbs and leaves that one on as a soft, warm light. Nightlight On turns off all but two bulbs, and leaves those on at very dim levels (just enough to see by). And Dining Room Off turns off all the bulbs entirely.
If I nest it into a group, it will always turn off all the bulbs completely.
[I just wanted to edit this post and link to the solution I found to my particular problem. It’s working wondrously for me. A Satisfying Solution for Philips Hue Scenes, SmartThings, and the Amazon Echo ]