Hi @AlexG, thanks for your feedback! 
Well, it doesn’t exist yet, indeed, for now the best solution is to create a room for each « group » you want (you can create fake rooms if needed), and then turn on the room.
Another solution is to create a « fake device » by creating a device in the MQTT integration (a lamp).
Then you create a scene that when this device is turned on, you turn on the lights you want, and when the device is turned off, you turn off the lights you want
Better than a room-by-room view, we aim to have multiple dashboards, to be able to separate different dashboards.
If you want to see this feature in Gladys, don’t hesitate to vote for the feature here: