If you have a micro SD card inserted, the two middle function options (FS and FL) are enabled and if pushing “M” when FS is selected, a wave form should be saved. FL is for loading a saved waveform, also with “M”.
It doesn’t work for me (gives “SD Card Err”), but that might be because the card I use is too large (4GB). I’ll try to get a smaller one and try it again.
Mine doesn’t show up as anything (on my Mac), but that might also have to do with the SD card being too big.