Most BMS players support Base10 (00-99) and Base16 (00-FF) channels. I don't want to deal with number clashes in the future, so I took the liberty to extend the support for channel numbers into Base36 (00-ZZ).
This allows more meaningful channel names,
#xxxSC for scrolling factor and
#xxxSP for spacing factor.
Speed and Scroll Segments
#SCROLL01 1 #SCROLL02 0.5 #SPEED01 1 #SPEED02 0.5 #001SC:01020102 #001SP:01020102
Speed and scroll segments are introduced in StepMania 5 to dynamically change notes spacing and notes scrolling speed. This allows scrolling effects to be created without relying on BPM changes or STOPs.