- Turn the Underlay on for the Level that shows the items you want to Tag
- Tag the Item/s
- Use Linework tool on the items that you have tagged. This is important - if you don't do this, then the Tag will disappear when you turn the Underlay off. *However*, you can use the Linework tool with Invisible Lines (if you don't want to see them) - this will still force the element to be considered by Revit when it determines if it should keep the Tag visible or not.
- Turn the Underlay off
- Your items are still Tagged!
Interestingly, if you use the Linework tool again, this time with By Category on the lines you previous selected, then the Tag will immediately disappear (Revit is no longer considering the object when drawing the view).