I may be wrong on this, but I don’t think you can send a single material file to a palette because since there is not splices, there is no .mafx file, there is only a .gcode file. But once again, I’m not certain.
If you use Accessory Mode, You may just want to press the download button next to the “Send to device” button. From there, move the .gcode to the flash drive or SD card that goes to your printer, and move the .mafx to the flash drive that goes to your mosaic palette. Then, follow the steps on the on the palette, and you should be all set.