The first step in the process is to change the normal vector in the
"MapToPlane" module. Since we want an XZ cut we need to make y
normal direction by setting [0 1 0] as the input value. Next
you'll need to connect a "Scalar" module to the left most input tab of
a "Compute" module. In the "Compute" module set the Expression
field to a*[0,1,0] which will multiply the scalar input value times in
the vector to define a starting point for the cut plane.