group_label parameter enable you to combine fields into custom groups, within a given view, in the Field Picker. Consider this example:
If you did this, instead of the fields appearing un-grouped, they would be combined into an expandable Shipping Info section:
group_label also interacts with dimension groups in useful ways, since a
dimension_group automatically places its fields together in the Field Picker. By using
group_label, you can add additional fields into the dimension group. For example:
This would look like:
Please keep in mind that you can’t group dimensions and measures together in the same
group_label. Within any given view all dimensions always appear above all measures.