I am experiencing a similar issue and hoping to get some feedback on how to best address. 
  
Setup:  
- My Insteon setup uses the ISY-99i/IR Pro for all communications (i.e. no "device-to-device" control; everything goes through the ISY). 
- ISY is firmware 3.2.6 
  
Devices:  
- I have a lamp connected to a LampLinc which works great.   
- I also have a KeyPadLinc which has button "G" configured in toggle mode to control the LampLinc, and that also works fine. 
  
Objective:  
- My intent is to create a scene on the ISY where both the LampLinc and the "G" key on the KeyPadLinc are controllers.  This would ensure that the toggle state (on/off) of the KeyPadLinc button is updated when another device is used to change the state of the LampLinc.   
  
Approach:  
- I created a scene on the ISY.  I added both the LampLinc and the "G" button of the KeyPadLinc to the scene.   
  
Issue:  
- My issue is that the ISY interface will only allow me to add the LampLinc as a responder (not as a controller).   
- I can however add the "G" button of the KeyPadLinc to the scene as a controller. 
  
Question: Is it possible to add the LampLinc to the scene as a controller?  If so, how?