Click on button and input group name.
Long press the desired group to enabled "delete" button. Then click on the "delete" button to delete a group.
Click on a group and enter to the group detailed page.
Click on button to choose cameras from device list.
Long press the favorite cameras to rename, input the new name and save.
Long press the desired camera to enabled "delete" button. Then click on the "delete" button to remove the camera from a group.