Hello,
In Webdynpro we don't have screen kind of thing in this we have View/Window and navigation done between those using Plugs.
https://www.google.co.in/#fp=699195f1bcac1587&q=navigation+in+web+dynpro+abap
for more related to leave screen,
https://www.google.co.in/#fp=699195f1bcac1587&q=leave%20to%20screen%20in%20abap
BR
Chandra..