What file stores ME payloads?

[WytchCrypt]

Hey all, I'm trying to keep an old Hornet mod called Smokewinders working.  It hasn't been updated in a few years and old payloads I defined with Smokewinders still work in the game, but the ME won't allow me to add Smokewinders to any new payload or change the color of ones I already defined.  I want to debug this and have been searching but can't seem to find the actual file where mission "payload" definitions are stored.

Can anyone help me out?

Thanks!