How Create Event OnResize??? Is Possible?

Get Game User Settings → Bind Event To On Game User Settings UI Needs Update

This doesn’t work with Editor Viewport size changes only when using Standalone Game or actually building the project

Maybe this works with editor viewport size changes :

GEngine->GameViewport->Viewport->ViewportResizedEvent.AddUObject(this, &MyObj::MyFunction);
void MyObj::MyFunction(FViewport* ViewPort, uint32 val)
{
}

It’s from this post: