Click and drag the black points to reshape the object just like you would in the Scratch Vector Editor. Adjust the sliders to your preference.
I really wanted to try and recreate the reshape tool so that's what I did. My version isn't exactly like the reshape tool in the Scratch Vector Editor as you don't click to make new points and is (for now) limited to 20 points but I am still happy with how it came out. Everything made by me. ( @jackbotic )