WebPlus X6: Import/copy content or pages

Greetings
How do I copy content from one website into another?
I have content I have developed and have the Site1.wpp and want to copy portions of it into Site2.wpp
I have found NO way :(
It seems only ONE *.wpp can be opened at a time.
The only one instance of X6 can be open at a time
That a *.wpp can not import another *.wpp as attached, (added).

How to I copy content of portions of some site, into portions of another site?

thank you,
alan