Attached is a .zip file of the .py plug-in that allows you to quickly select diagonals (of a specific horizontal width) to delete to reveal underneath layer to make your handdrawn plaid pattern.
also shared to gimpchat.com: http://gimpchat.com/viewtopic.php?f=9&t=...ls#p292483
also as point #15 on https://plaid-patterns.com/related.php