How to force/specify which variable Assembler uses as "x-axis variable" for plotting?

Hello! I cannot figure out how to force/specify which variable Assembler uses as "x-axis variable" for plotting, when using corners for doing sweeps.

I have prepared the following "toy example" that describes well the problem. I have a maestro view which a single test that does a single-point DC simulation of an NMOS, and calculates the gm from the opPoint results. The gate, drain and bulk voltages of the NMOS are defined by the variables VG, VD and VB, respectively.

I also have 3 corners in my view:

• "CornerA__fixed_VD" = a "single-point" corner with an explicit value for the VD variable (<---this models a single-point corner used in my real-life application for some sort of calibration condition)
• "CornerB__sweep_VG" = a sweep of the variable vG (<--- this models an actual sweep of a parameter, as I would normally be interested in doing)
• "CornerC__sweep_VG_at_explicit_VB" = a sweep of the variable vG too, but this time also with an explicit value for variable VB.

Here are 2 cases, with and without the problem:

• Case #1: If I run corners A and B together, and use the "Plot all" option from the results, Assembler uses "VG" as the independent variable for plotting, and I get a nice trace for the results of the sweep. 
• Case #2: However, if I run corners A and C together, and plot as before, Assembler uses "VG" as the independent variable for plotting, and as a result I get a nonsensical plot with the results of the sweep scattered across several traces.

So, how can I force Assembler to plot w.r.t. the "swept" variable "VG" in Case #2, just as it does for Case #1?

Thanks, Adam.

Note1: Please note this is a toy example: I know there are other ways to do sweeps, but the one I describe here is representative of the actual situation I encounter in my real scenario.
Note2: I know about the "Swap Sweep Var" in VIVA, but unfortunately this doesn't solve my problem, as I would need to manually do this each time, which is not practical in my real scenario (Plotting Templates doesn't help either, they seem unable to work with traces created through the "Swap Sweep Var" method).