I put this off for a while because of finals and all that, but no, it still doesn't have a palmask.
Those two buttons I circled are your friend. Quoted from the Lunar Magic help menu:
"Palette masks provide a method for palette files to specify which colors in the palette should be imported into your level. In this mode, you can mark which colors should be enabled or disabled for export with a Left Click (add Alt for an entire row). An X means the color is disabled, otherwise the color is enabled. When you export the palette to file in any format, all the colors are technically still exported regardless of the settings... but if any colors were disabled the settings are saved to a separate .palmask file that goes with the palette file of the same name. When you later import the palette file, the program will check for the presence of the .palmask file. If it exists, it will load the settings in it and only import the colors that were enabled into your current level's palette. If it doesn't exist, all the colors are imported.
Note that palette masks are automatically cleared whenever a new level is loaded. And the only way to save them is to export a palette. You can use the Palette Mask Menu button to quickly enable or disable all colors for export."