In this thread:
It makes it sound like Quicken has Hierarchical tags. Quicken Windows certainly doesn't have them. It isn't clear if this was talking about only Quicken Mac or all versions of Quicken, so it begs a question if Quicken Mac does.
You can certainly do enter tags like House:Basement in Quicken Windows, but this isn't Hierarchical.
This is just the syntax to show that both the tags House and Basement are on the same transaction.
If this was a category which is Hierarchical then House:Basement would be a separate category different from either House or Basement.