Broadcasting changes to many blue 2-1 switches at once (ZHA)

Background – Many Blue 2-1 switches, HA using ZHA.

I have scenes “Rise and Shine” and “Time for bed” in HA. The two of them control a helper that basically tracks if it’s daytime or night time for me, based on which one was triggered more recently. I would like them to change the LED intensity of all the switches – dimming them at night, bringing them back up during the day.

My guess was that the best way to do this would be a zigbee command to a ZHA defined Zigbee group containing all the switches. (Presumably Inovelli_VZM31SN_Cluster / led_effect command). But I can’t figure out how to format and send the command.

Would appreciate help.

(A similar thing I’d like to do is update defaults on all the switches simultaneous; get them all to have default fade speeds, etc.)