One option is to change the Building Material Intersection Priority of one of the walls so the horizontal wall is stronger than the vertical wall (the horizontal wall will cut the vertical wall).
David
David Maudlin / Architect www.davidmaudlin.com Digital Architecture AC27 USA • iMac 27" 4.0GHz Quad-core i7 OSX11 | 24 gb ram • MacBook Pro M3 Pro | 36 gb ram OSX14