Hello didgeridoojedi
The Curves are also editable for Env mode, there are less options, only two modes percussive and normal.
It is so because the Cyc Env in Env mode is not the same envelope than in run/loop (different sound and behavior)
If you really need a flexible envelope i recommend using the Shaper LFO, there you will be able to draw any shape and curve and adjust it to the desired effect.
Hope that helps.