How to draw polygon in Slate or UMG?

Hi, I have created a custom UI class, both Slate and UMG, they are SFenying(Slate) and Fenying(UMG), now I want to draw polygon in the custom UI by user clicking mouse, and I find some c++ function in HUD can do this, but in Slate/UMG, I have not find some thing, is there some idear?

You can either use FSlateDrawElement::MakeCustom and provide an object that draws directly on the RenderThread or FSlateDrawElement::MakeCustomVerts, which allows for instanced rendering of a custom set of verts.

Are there any examples for that somewhere?