I like to use the expression pedal to control multiple Amp/FX blocks at the same same, however I might want the start and end values to be different depending on scene.
Scene A may well be a clean setting on an amp and I might want to swell into a clean lead tone by change the eq levels and the volume by a few DBs.
Scene B I want to the start the gain a bit higher (crunch) and then swell into a higher gain tone with the volume increase being a few extra DBs.