Yes, it is certainly possible to use Sunday Guitar and Sunday Keys patches together. You don't want to have more than one MainStage concert open at once, or the concerts become corrupted.
The way we recommend to work around that is to build your patches in Sunday Guitar, export those patches to your computer, then load them into Sunday Keys and map them to Section 5.
If you are trying to combine both visual workspaces, you may want to reorganize/arrange the visual aspects so that it makes sense for a dual setup.