Copy shading/light group assignment to many lights

I have a couple of hundred temporary area lights in my scene (big office space) and I want to assign them to a lightgroup. Selecting many and assigning don’t work (via alt key). Ctrl+C doesn’t give me any options that appear logical, pass index didn’t work. Ctrl+L allows me to link object data, but that doesn’t include this setting.

Is there any way to get this done? Maybe a script or something? I have no idea about scripting at all.

maybe this:

Yay, the “Set Light Group” button worked. Not being able to assign while holding alt sounds like a bug/oversight though. Thank you.

yay = tear the roof off the mother sucker