If the software is the MXEditor and you cannot figure it out, good luck.
Do not know if it is the same software for the MX-700/ Mx-800 (circa 2007). I have used that for many years to update many pieces of equipment. I have found for newer equipment it is best to learn it from the equipment's remote. I thought their instructions were good in the user's manual (mine is 72 pages) Since they do not let us "amateur" user's update the software. Mine only works with Windows XP. Learning can be tedious but it works well, worked with my ROKU4.
I would suggest to start from scratch (AS PER THE other post). And if you want to add any custom commands you may be able to download other .mxf files from remote central.
My Mx800 is old but it still works and with all my new and old equipment. (even can control my HTPC, mostly) The software is the key.