Hi @Hasturo,
The tutorial were written for OH2.1 and before @rlkoshak recomended me to change to roomname_ whatever syntax. So these days I am rewriting it. Main thing is that now we can use Member of Group as rule trigger and use triggeringitem, as well as use split((triggeringItem,"_").get(0) to get the associated item: Design Pattern: Associated Items
However it should work as intended as listed above,
The idea is that you put your lights into groups, all lights in livingroom belongs to that group, however you might have a group called livingroom_relax which then is a subset of your lamps in the livingroom.
The scene item is just for the sitemap which then lets you select the correct scene, the idea is that to make it as generic as possible 0,1,2 is predefined, above you add ur relax scene and so on…
The lambda function(where all the magic happens) takes the room group, and the scene group. The third parameter is hsbValue, maybe @rlkoshak can come with some input here. The idea is that in many cases(like your relax mode) you would like to dim your light to 50% and turn the light more yellow. hsbType can store both these information with a single item, hence the third parameter. I am unsure if I can make it optional somehow, to simplify it for lights with just ON/OFF.
I expect to update this tutorial by easter! But feel free to use it as it is for now.