The ID of the group is a number of the group, which is necessary for arm separate groups from the keyboard.
The group number (ID) is displayed in the group settings (Hub → Settings 
→ Groups).
What is the identificatior (ID) of the group?
Updated
The ID of the group is a number of the group, which is necessary for arm separate groups from the keyboard.
The group number (ID) is displayed in the group settings (Hub → Settings → Groups).