-> right click on group
-> hover over render style
----> disabled: group is locked
----> invisible: group is invisible
----> ignore: group wont be included when you compiler the map

These 3 flags can be combined freely. E.g. when you worked on a levelpart, you can set disable and ignore so that you can see it in the editor, but you cant edit it. When you compile the map, it isnt included because you are only interested in the new group you are working on.

I guess this helps.