Is it possible to tag a shaft opening?
Which elements are not able to be tagged?
I don't know all the list of elements that cannot be tagged, but at least Shaft Openings are one of those.
Alternative: Create a detail component family. Something simple, such as a rectangle with an "X"; put it inside the shaft, and then tag the detail component with a multi-category tag.
See illustration.
I'm in Revit 2019 - I was 'Grouping' my Shafts, with a suitable name, hoping I could schedule them,
which you can, but Filtering the schedule is an issue as it does not seem you can add a Comment Column.
So, I tried to Filter them using the Group Name, but you can't do that either.
No doubt Revit 2020 it will all be well, holding my breath in anticipation.