The filter based on element is not working when the control uses a composite condition or action.
This is a known issue in V8i.
Starting with the CONNECT Edition, if you filter by element, controls will be displayed even if the element is part of a composite condition. To download the current version, please follow the steps found in this link.
As of 10.00.00.50, composite actions are still impacted.
For the issue with conditions, if you are not able to upgrade, the following workaround can be used. Go to the Conditions or Actions tab in the Controls dialog. Here, go to the Type pulldown menu and set this to Composite. When you choose the element from the Condition Element pulldown, the list will be filtered to show controls with that element as part of a composite condition.
Reference # 495379, 655276
Creating Controls - Composite, Action, and Control Sets - WaterGEMS and WaterCAD V8i SELECTseries 6 and CONNECT Edition
Creating Controls - Conditions, Actions, and Control Sets