If I remember well (I don't have access to my scope system ATM) you should have to go to the "key group listing panel" and then open the panel called "option".
There are two evnvelopes called 1 and 2. (watch in the lower right corner) The first is a simple ADSR envelope and it's used to control the VCA of the sampler.
Yes i got that. Thanks for this, however my question is not how to find ADSR controls. I know where they are. But how can i control them live. AFAIK some parameters are already assigned to some midi CC but decay is not. Is there any way to control decay on that first ADSR envelope via midi CC?