I think I know what you’re after. What Meris calls Envelope Down (like a Mutron III Drive Up / Down). I call it an inverted envelope, or peak follower. It takes the shape of your input signal, and turns it upside-down.
The bad news is: You’re not going to get that in the H9 Flanger. Useful feature; it’s just not there. Changing the Shape to ADSR will get you a fixed set of triggered envelope controls, but it’s not what you’re looking for.
Let me give that some thought on ways you might get around that; either externally, or by using another algorithm for similar results. And I still owe you more presets, & an explanation to your earlier questions.