In the past I have added a field like new_window in on the rffNavon and rffNavTree content types.
Then if I field new_window is set to Y, the managed navigation code would open the landing page link in a new window.
Another way to do it is to use the type of link template in the Managed Navigation Slot rffNavLandingPage.
So usually you might want a file content type to open in a new window.
Using the FFWD content type rffFile it would use a snippet template called rffSnTitleLinkNewWin.
<body style=“background-image:none; background-color:#ffffff;”>
<a href="$pagelink" class=“titlelink” target=_blank>
This macro landingPage_Target will inspect the template you use in the rffNavLandingPage Slot to see if it opens a link in a new window, by seeing if it contains target=_blank.
Put this macro in user User Velocity Macros
##Code to figure out if the Landing Page opens in a new window
#set ($slotContent="#node_slot($node ‘rffNavLandingPage’ ‘’ ‘’ ‘’ ‘’ ‘’)")
Using this macro from common Managed Navigation Code
#set($landing_page = $node.getProperty(“nav:url”).String)##
<a href="$landing_page" #landingPage_Target($node)>$title</a>