To modify a cable tray that is inserted on the drawing, go to
Ribbon: DM Electrical->Devices-> 
Query Device
Pulldown Menu: DM Electrical->Modify Devices->Query Device
Select a cable tray centerline on the drawing. The information in the database regarding the selected cable tray will be displayed in the Edit Cable Tray dialog box.
Edit Cable Tray Dialog Box
Changes can be made to the cable tray in the same way as when it was inserted. See the Insert Cable Tray section for more information.