Corel DESIGNER 2018 doesn't weld/trim/simplify/... objects

As my title, I am new in Corel DESIGNER and using ver 2018 now. I create two rectangles and use Objects/Shaping/Weld but the two objects remain there. The same to Bordering, Trim, Intersect,...

But when I use Combine (Ctrl+K), it's OK.

Can anyone help? Thank you.