On page 43 of the G-System manual it says that you can use encoders A, B and C to control parameters like feedback from a delay effect. I have been trying to figure out how to do this without any success. For instance, I'm trying to use Encoder B to control the delay feedback. How does this work?
Using the encoders A, B and C as modifiers is a bit special and not very commonly used. These encoders can be assigned to control a parameter in the modifier page, but they cannot be used in PLAY mode. You have to pass in EDIT mode to get control. You need first to assign encoder B to control the delay Feedback in the same way as you would do for an expression pedal - This is done in the modifier page - then store the preset.
When performing, your unit is normally always in PLAY mode, and this allows you to recall your presets and activate/de-activate the effect buttons. In this PLAY mode the encoders are not active -If you load the specific preset (of your example) and turn encoder B, there will be no feedback control. If you want to control your delay feedback with encoder B, you need to temporarily pass into EDIT mode, and then turn your encoder to control your feedback parameter.
Don't forget to return to play mode if you need to get back to normal operation.