Canno resize anything in widget editor [UI] [UE 5-01]

version: UE 5.0.1

This is a little widget blueprint whose parrent class is merely a subclass derived from UUserWidget. However when I open it in the widget editor and try to add some text blocks and other things, I found only the green boundaries with no anchor points and I cannot resize or move any component as in the UE5 documentary and some tutorial videos.

Anyone know how to move and resize widget components in UE5.0.1 or what is wrong with this?

I should have put a canvas panel instead of a border at the beginning