Sculpt Smooth Brush with Shift + LMB

Hi, in Blender 5.1 the smoothing in sculpt mode got this "Temparary Brush Toggle Type" rather than "Stroke Mode" in 5.0 and under. I wonder if what is this for. I wish this one goes back to old one as the keymap I saved don't recognize it. thanks {attachment '7k3j.{media' does not exist}