Thank you. I didn’t understand well the algorithm( I usually don’t read the instructions: shame on me). Now I see better.

For the pan, I understood how it works.

About the separate feedback control, I think it should be a completely different algorithm: I imagined a delay with a kind of simple pattern of normal and reverse repetitions.

For example:

(left)wooap (right)pop pop pop …

It’s really something else, another algorithm. So it’s an idea to put in a corner for later.

About modulations or filters. A low-pass filter on repetitions is always nice on a delay: the delay becomes darker as it goes.
As for modulation, there’s plenty to choose from (flanger, phaser, chorus, vibe, distortion). But spontaneously, I’m saying more of a phaser or vibe.
But you (we) have to think about it: it need one original idea that works well with the zig-zag concept, not plenty of parameters. In my opinion: the simple and powerfull the algo the better it is.