Hello,
Here are some links found after a quick google research about ue4 umg resize :
Tutorial: Move/Scale “Window Widgets” | timmahw as tutorial.
https://www.youtube.com/watch?v=04t1RucNk4w as a video
GitHub - MWadstein/UMG-ResizableWidget: Resizable Widget for UMG for Unreal Engine 4 and its downloadable project.
I am sure you can find a lot more by a few mins dedicated time. I haven’t check more than first ones.