The online document states the itinerary designer can be found from root folder of BizTalk 2013 DVD.
The itinerary designer for ESB Toolkit
The itinerary designer for the BizTalk ESB Toolkit is now part of the BizTalk Server installation media. You can find the itinerary designer at the root folder of the media and has the name Microsoft.Practices.Services.Itinerary.DslPackage.vsix. Earlier, this file was available at the location where you install the BizTalk ESB Toolkit, which typically is \Program Files\Microsoft BizTalk ESB Toolkit.
What's New in BizTalk Server 2013
However you may noe able to find the file from various of sources(installer DVD, biztalk & esb installation pathes, etc) in case you install the RTM build downloaded from MSDN subscriber site.
BizTalk production group stated they have now integrated dev tools (ESB Itinerary extension) as part of the ESB setup as well. So you do not have to manually install the ESB Itinerary designer anymore. They had the issue in Beta where the setup wasn’t creating the project extensions. So, they had placed the vsix file as part of the media and documented it in our release notes. We have fixed the issue since then, and you don’t need to manually install from the vsix file in base media anymore.
To resolve the issue, please try running:
(in a command lind of VS2012 directory)
and then check again.