I ran across this following experiment about the type of item to use to mark your own patterns on the mylar sheets.
Only 2 of the 6 types of markers were able to be read by the knitting machine electronics.
Results: the regular lead Med pencil AND the HB pencil.
I tested the marked sheet and the results were the same.
I also erased a section. The one with the lead pencil erased adequately. The other pens, didn’t budge.