Yes Samuli, I am wrong.
I was trying to build my ASSIST as the main Controler of my current WDA and more generaly, for several WDA that will use and instanciate my ZCL_WDA_CTRL as ASSIST.
In fact, I am trying to find a way to optimize and use the runtime instanciation to have only one Controler (ZCL_WDA_CTRL) for several WDA.
This Controler will live outside any WDA context ... I suppose that is not the correct approach...
Well, thank you again Samuli for this help.
Rachid.