To delete the groups:

1. Select the groups you want to delete in the Table of Groups in the left part of the screen. Multiple items can be selected by dragging or holding CTRL or SHIFT while clicking.
2. Click Delete button from the Main Controls to delete selected groups. You will be asked, if you really want to delete the group(s). Click Yes to confirm.
3. Click Apply to keep changes or, when prompted to save changes on exit, click OK to confirm.