I just created two offset alignments in a test drawing and ran the superelevation wizard on both of them, just as I would for a centerline alignment. Were you trying to do something else?
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The original error from superelev wizard was that the offset alignment did not have a design speed.
This speed was lost when I changed the start station to a range different from the centerline.
Now I made a test alignment too and created the offset alignment and I can run the superelevation wizard with no problem but The design speed of this new offset alignment is different from the centerline (100Km/h vs 60Km/hr).
After more testing I found a way to change the speed and the design criteria and is by setting the "update mode" in Offset Parameters tab from dynamic to static.