flexi-bot/docs/marlin/_gcode/M221.md

tag	title	brief	author	group	codes	notes	parameters	examples
m0221	Set Flow Percentage	Set the flow percentage, which applies to all E moves.	thinkyhead	motion	M221		tag optional description values S false Feedrate percentage tag type percent int tag optional description values T true Target extruder (requires multi-extruder). Default is the active extruder. tag type index int	pre code Set the flow rate to 150%. M221 S150

Set the flow percentage, which applies to all E moves added to the planner.