[Closed] Material Plugin: How to Keep Material as sub-material upon creation

I have a material plugin which extends the Blend Material and replaces its UI.

If someone has a material in their compact material editor and chooses to click to change the type to my material there is no prompt asking whether the user would like to discard it or keep it as a sub-material like there is when you do the same thing with Multi-sub material etc…

Is there any way to add this to a script material plugin?