Thanks for the advice. I'm finding one part of it confusing, though. Both of you, David and Kbird1, have said I need to be careful getting things right in the vertical. But when stair sections are joined using a landing, and they merge into a single object, HD Pro handles the Z relationships for you -- joining one section to the next and representing them as "Section # 1-1, 1-2, 1-3, ...".
It sounds to me like what I'm hearing from you is that there is not an analogous merging if there is no landing. Instead I must manipulate the vertical position of each section independently myself. Is this right? How does one even set the vertical start of a stair section? I do not find a "Distance from floor" field on the stair dialog, and HD Pro's Transform/Replicate dialog seems to ignore an attempt to shift a stair section with a "Z Delta" move.
Thanks again for your help. Really appreciated.
(P.S. Since this is a tough -- but not uncommon -- thing to need to do in HD Pro, it seems like a good topic for a tutorial video, no?)