"Custom" waypoint available through scripting?

[Wrench]

Hey all. I'm trying to use the "custom" formation type for ground forces, while adding waypoints via script. I'm currently using MiST. The function function mist.ground.buildWP() does work, but there is no "custom" option. 

I have used the custom option on waypoints inherited from the ME to great effect, such as having infantry move in a reasonable cover formation. Something like this:

The issue is when given waypoints via script, that option is no longer available.

 

Does anyone know how to get MiST to do this, or know of a similar function I can use that preserves this?

[Wrench]

So I found that if you have the 'custom' type set in the mission editor, you can just replace the ["action"] part of each waypoint with 'custom' and it works.