It's showing on my version. What version are you using? It's spelled "Knightmare", in case you were looking for it under Nightmare.
Ah, that would be why! Current version of the sheet is V1.17 for players, and V1.16 for the GM sheet. Current player sheet: https://docs.google.com/spreadsheets/d/1HG2urf-4l6qa7uQehIKUPA1ehPDwjxcHAWClh-hj...