As one Architect told me: “Revit does not do corner windows”. This is indeed so (openings have to be created and custom families created), and the same may be said for curtain walls, especially when they are embedded in walls and meet at a corner. Either a void has to be modeled in place and cut from the corner join, or the wall profiles need to be modified. The video below illustrates this and then goes on to show how to create a silicone joint or to switch that to a corner mullion. Come and do a course at Micrographics and learn more about curtain walls and other interesting Revit skills.