anyone know why a custom transaction wouldn't allow negative amounts? It doesn't make any sense that you can't use discount items/negative amounts when you can on every other transaction.. its fails in the UI and script and netsuite claims thats how it works but it kind of isn't since it works for the other types

I ran into the same thing. Expected it to work and no dice

did you contact support at all or get any answers by chance?

No - error message was straight forward, so I figured I was just trying to do something that they didn't want to allow for some reason.