Vertical Wall Connecting Ceilings

[JCKC2010]

I am using Home Designer Pro 2021 (pretty new to the software).  I have created ceiling planes over 2nd story room that have a railing overlooking the lower living room.  The ceiling plane over the second story room has a different pitch than the one over the lower living room they both meet at the top to keep one ceiling line vault.  What I need to complete this design is a small vertical section of wall to fill the gap between to the 2 ceiling planes above the railing(see image below). Any help in steps to creating that wall would be appreciated.      

[solver]

Select the circled wall in elevation and reshape it so it fills in.