I'd say keep it simple - for example; call the main chart area the "Main Panel" and, all other panels, whether above or below the "Main Panel" would be referred to as a "Sub Panel". Sub Panel means subordinate to, and not necessarily, physically below, the Main Panel. So you would always have the Main Panel along with however many Sub Panels you want, either above or below the Main Panel.
The indicators could then be placed on the Main Panel, or in their own separate Sub Panel either above or below the Main Panel as you desire. On the Chart Indicator Selection Window, you can group the indicators as "Usually on the Main Panel" or "Usually on a Sub Panel".
