Custom grouping and custom commands is limitless. For eg I have 3 lights in the study (Study1, Study2, Study3) which I can control individually. These are grouped as "Study lights". Then they are in another group "Upstairs" and finally in group "All lights". By using groups I can control an individual bulb, or all 3 in the study at once, or as part of any of the other 2 groups
I really wish they would add this for multi room music on echo devices.
I can't create an everywhere group and then separate upstairs/downstairs groups.
Each Echo device can only be in a single group for multi room music so if I create an everywhere then that's it.