I've been 'playing' with this feature and uncovered what I feel is a 'bug':
Have created a Group "MX-Uplink" with three VLANs
Applied this to the Allowed VLANs field.
All good so far.
Now, if I go and amend the VLAN list against the group I was expecting that to be reflected in the port configs that it is applied to.
That is not the case, you have to go into the port config and select the same VLAN group again and this time it updates the allowed VLANs list.
So what is the point of having a Group if when you amend it, it doesn't update the ports that its applied you - you still have to go and manually update the switchports that its applied to.
Am I missing something here?