Updated for 7.0
On the left-hand side of the screen in the navigation bar under Member, select Group(s). This will take you here:
In the table titled List, scroll to find the group you wish to edit.
Click the name of the group you want to edit. This will take you here:
Under the box titled Sr. Lieutenant(s), find the name of the group LT you want to remove.
To remove them from the group, select the red button with a trash can icon to the far right of the screen in the same row as their name.
These are samples.