Hi support, this is a bug report.
The bug is that the basic theme does not display grouping in queries correctly. Here is an example screenshot from the CRM application (Correspondence grouping):

As you can see in this screenshot first of all, when a group is expanded no - sign is visible on the grouping "row" (first group in screenshot) and when the group is collapsed there are + signs all along the grouping "row" (second group in screenshot).
Thanks