Service/action for manipulating group members of new style groups

[russilker]

Hi! This was already asked in a closed feature request, but the solution there won't work for my use case so I think it makes sense to re-open. Having a service/action like group.set, but one that works for new style groups and not just old "group.*" domain groups. would be huge for me.

My use case: A "bedtime" mode that, when turned on, stops all but one specific light in the bedroom from being used (creating a dim ambiance instead of blinding us with bright light). We have three control mechanisms, all targeting the new-style light group: A smart light switch, Alexa voice control, and a button in the HA app. For example: When bedtime is off, flicking the light switch, saying "Alexa, bedroom on", or tapping the button in the app would turn on all of the lights in the bedroom. When bedtime is on, the same commands would only affect one bedroom light, leaving the others off. To accomplish this, I would need the ability to add/remove group members using the proposed service/action in an automation.

In the closed feature request I linked above, the proposed solutions of labels/templates wouldn't work for me, nor could I use the classic-style groups that support the group.set action. This is because of voice control through Alexa: We still need to be able to manipulate bedroom light color and/or brightness with a command like "Alexa, set bedroom to 50%", which requires the newer-style light.* group. I also can't leverage Alexa's native groups because I can't add/remove group members from them on the fly using automations. I tried to work around this by using the Spook action to disable/enable light entities/devices as needed, but this doesn't seem to work right-- after re-enabling the entities (Zigbee bulbs over MQTT), it takes a good 30 seconds for them to come back and also causes all MQTT devices to briefly go offline for some reason (maybe a separate bug). Even if this worked, this isn't ideal as it leaves them completely unusable when bedtime is on, while the proposed solution would just remove them from the group and still allow them to be toggled individually if needed.

I feel like I wrote too much as it is, but happy to go into more detail as needed. :)