Under the M1010 section, S10 sets the enclosure door flag as open, and S11 sets the enclosure door flag as closed, regardless of actual door position. S12 reads the sensor and resets the status.
While it should be for advanced users who understand the safety implications, it can allow users to run larger than enclosure things without having to actually remove the enclosure. It also allows users to use their enclosure, even if the door sensor is broken by setting the door closed.
EDIT: I had documented this finding here.