You sure can! To create a Word (.docx) file to share with an editor or reader, go to the main File menu and select Export Content As > Word File…
This exported file is not intended for publishing. However, all of the content — including any front and back matter you’ve added in Vellum as well as the basic structure — should be represented in a way that will be maintained when you import your book again.
You can learn more about Importing Your Manuscript in Vellum Help.
Still have questions? Contact us.