GJ: Storage quota limit for files and images

There's only limit for no. of uploaded files and other file types.
This is not so helpful for what we do.
Is there a way to use Auto Action to eg. sum up the size of uploaded files by a counter or so and then sending a notification?
We'd like to set a quota of up to 4GB for specific group categories where a typical file size is often equal to 0.5 GB.

There's no quota limit functionality in CB GroupJive. You'd have to completely implement tracking of that and try acting on the before create triggers for GJ files/photos to validate and the after create triggers to increase the stored quota for that user.