(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 wants to use LMRKLIST1.TXT when it does not exist, it either uses LMRKLIST.TXT or creates LMRKLIST1.TXT from LMRKLIST.TXT.