Checking the current variant of the custom object your working with is crucial.
If i wanted the shapepainter in my 1 variant to be red, i cant do that.
solution:
add conditions and actions to deal with the variants
What do you mean by variant? Are you saying copies or instances?
With custom objects you can add your own properties, actions, conditions and expression.
If you create a property, you can click the 3 dots by it and GD will add functions to read and set the property. You can then modify the functions to read/set the shape painter settings.
I do wish there was a way to access children objects directly by using the custom object name then either a period or colon followed by the child object name. Something like MyObject.ShapePainter…
this is not a variant, the new GDevelop custom object property, variants.