It has become common to see posts that suggest the use of Dynamo for things that Revit already does. Do not overcomplicate this matter. If you need to have a tag that you can schedule you have basically 2 options:
1) Option 1 is an annotation family with two parameters, one for the "ID" of the element, another one for the Description of the id number or letter. The annotation symbol is just a circle or square with a label inside that is tied to the ID parameter. In the project, place as many of these annotation families, and then create a note-block schedule.
This option 1 is useful when you need to tag something that does not have a host. And by this I mean that Option 2 is a tag that needs to find a host, such as a wall, a desk, etc. Option 1 is a tag that can be put in the middle of nowhere. Option 2 needs to be pointing at something.
2) Option 2 is a keynote tag. There are 3 kinds, User Keynote, Element Keynote, and Material Keynote. I suggest that you read in the Help documents about the details of this topic. This tag can be schedule with a Keynote Legend, and it can be filtered by sheet, which I think is what you are looking for.
Alfredo Medina _________________________________________________________________ ______
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