Just a follow-up to note a couple TurboTax (Win desktop) behaviors and indicate my final decision after another Program Help session with a very helpful TurboTax rep:
With a shared screen, we started from my return with a modified name version of the TurboTax "de minimis safe harbor election" form (titled "Section 1.263(a)-1(f)..."), which had just my name and dba, and my SSN. We then used the Q&A method to opt for a de minimis election form within my wife's Sch C business depreciation topic, and noted that the existing election form just described was not changed, and a second election form (hopefully with my wife's Sch C info) was not generated at all. We also verified that a second de minimis election form could not be added from Forms Mode.
We then noted that my workaround of adding the "Blank Form" in Forms Mode, then filling it in to replicate my existing TurboTax election form (except for using my wife's name, dba, and her SSN), was indeed included in the "Official Forms for Filing" PDF generated in the Print Center (after setting up to e-file our 1040). She said that its presence there indicated it would be submitted to IRS as part of the e-file. Her confidence in this was high, noting that the "Blank Form" is sometimes needed to attach other statements or supporting details for certain tax situations.
So my final decision was to use the Blank Form to create a separate replica de minimis election form for my wife's Sch C business, and stick with my existing modified TurboTax election form for my Sch C business. This is consistent with the separate election forms I've filed in past years (e.g. TY2022 using TaxAct).
If anyone from TurboTax is reading this, future versions need to be able to generate a separate de minimis election form for each person on a joint return (according to my reading of the tax rules, and precedent).
