(Compiled by JRW)
Searching through the code, I can't find a specific use for LMRKLIST1.TXT. It appears to simply be a temporary copy of LMRKLIST.TXT that can be used import/export. It is updated by procedures that add and delete landmarks. If a program tries to touch this file, and it does not exist, it is either created from LMRKLIST.TXT, or uses LMRKLIST.TXT instead of creating it.