I guess I can also pull the resulting command that's generated (via Process Hacker) and turn it into a .bat file. As a bonus, I don't have to deal with the launcher constantly trying to update the modpack.
Err, so we get to complain about it not working at all? =P
Alright, fair enough. Though it seems like bad UX to me.
How do I go about adding args then?
Without this ability in Technic Launcher, the work around currently appears to be to switch to a launcher (e.g.: Twitch) that does allow me to break things as I see fit.