There is a convenient "Custom Builder" called "Graphene Junction" included in VNL 11.x and 12.2 (in 12.2 you have to open Tools>Custom Builder from the main VNL window). However it's also fairly easy to build in the Builder itself. Not trivial, but if you first study some of the Builder tutorials you should get enough experience to insert different nanoribbons and use the Move tool to fuse them.