I have added the tag schubert-calculus and begun tagging the numerous questions that should have it. Though this is a highly advanced topic usually more suitable on MathOverflow, Schubert calculus questions certainly do get asked. Those who frequent MathOverflow often go on this site as well and will often be able to answer such questions. I myself have asked a Schubert calculus question on this site and gotten an answer from exactly one of the few experts who needed to see my question.
As is often said, no topic is too elementary or too advanced for this site, it's just a matter of the audience you are expecting to read your question. Those studying elementary Schubert calculus at the graduate or undergraduate level may find it more appropriate to ask here as their work is not research level, though I don't think any Schubert calculus question would be turned away on MathOverflow.
Willing to entertain any objections but I doubt anyone will find reason to object.
Any assistance in tagging would of course be welcome.
Note: Based on Martin Sleziak's suggestion, I haven't done any tagging since that first day. Feedback seems to be mostly positive if you go by upvotes vs. downvotes. Not sure if I should be waiting for some sort of signal.
I will also note that this tag was used today independently of my tagging efforts. Not sure if the user saw the meta post (which is likely because it was featured for awhile), but it may lend some credibility to its usefulness: Schubert Cell Structure for some variety with prescribed bilinear form. The user had a Schubert calculus question anyway, and made use of the new tag.
Further note: I have resumed tagging questions as it seems the community approves. The only vocal objection seemed to be that I created the tag before asking the question, not a particular argument against the tag itself.