Landscape Blueprint Brush - Weightmap layers

The included example Landscape Blueprint brushes with the associated plugin have the ability to specify a weightmap MID, and target weightmap layer(s) to apply the weightmap MID to the landscape layer.

I’m trying to figure out where this logic goes off to, i believe it lies with the return of the Render function, and gets sent back to a parent CPP class or something.

I’m trying to expand on the functionality of it, by assigning different MIDs to different layers. Because at the moment it’s able to apply a MID to multiple layers, but only the one MID, where as i’d like to drive a splatmaps channels to different layers.
Anyone had experience with this? Or knows how to make heads or tails of source code to help me narrow down where the render function heads off too?

I’ve done a really convoluted work around, that i wish i didnt have to do. which solves the issue, but i’d still really like to figure this one out, so any info would be great.
I’m basically using multiple actors to solve the issue, but there’s a tonne of unwanted behaviour from this method, mainly they show up in the blueprint brush outliner, so it gets cluttered really quickly. and secondly it’s corrupting levels for some reason, if i save a level with a blueprint brush affecting weightmaps, the editor crashes on loading that level.