The SCM configuration includes a version specifier and this info is used at checkout requesting only that version.
If you want to share a single KB as working copy that will be used for projects that monitor and build different versions of the KB, there's currently no way to configure it: the first project that needs to checkout will do so for a single version.
Work-around: use GeneXus IDE (or MSBuild script) to checkout the required multiple versions. Jenkins projects that point to this working copy will just update their version on the already existing KB (won't need to checkout)
This was requested on GeneXus BuildAndDeploy forum: https://groups.google.com/a/genexus.com/d/msg/buildanddeploy/ZDj6kXjOEKA/vheDBCHZDAAJ