I don't understand your issue and I'm afraid that there is some possible confusion.
Files such as "boots.mlx" do NOT exist; I have created these files to help (from my point of view) the edition of the model list files (whose extension is .MLT).
Since I never documented the .MLX format I assume you are using them through shStudio.
When you edit and save a .MLX file, the four .MLT files (one for upper gear, one for lower gear, one for gantlet and one for boots) are generated. So without being sure it's your point, adding a set in a .MLX file will indeed generate a ????_foot.mlt, but definitively not a boots.mlx (and creating and empty boots.mlx won't generate anything since the mlx files generate their content (if they are empty) after analysis of the filename to determine the *** & class of the list.
Thank to describe your goals, attempts and results to allow better answers to your issue(s).
Edit: And of course, be sure to read

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