i had op in the room and i tried selecting it in the menu and /set mod
heres what i did to save it:
first i typed the name of the mod in the small chat box on the bottom of the window with a .tbm after it
then i clicked export
it then transported it to player exported mods and i moved it to data/mod
it showed up in the mod menu and it works in singleplayer, but not in multiplayer