(ie. I've tagged classes and want to filter a list of just the customers that have attended those tagged classes).
Answer: A form to create a segmented list contains filters for tags -- but for tags applicable only to customers. This form cannot filter by tags that can be applied to classes. You'll see an explanation of this in the screenshot below.
However, a workaround is to Filter by Visits (as in 'only show me customers that visited these classes).
Select Filter by Visits > Then choose from class type, class attended, template attended, or recurring class attended.
*Important*
If you choose to add more than one class, consider that in Step 1, the default setting is AND.
This means that every setting you choose below needs to be present in a customers attendance record in order for them to make this list. (As in, "show me customers that have done this AND this AND this. Only customers that have done all three of those things.")
If your goal is to see any customer that has attended any one of these classes, use OR instead.
For example, below, since we've chosen AND in step 1, and then listed two classes, then customers would only appear on this list if they'd attended both of these specific classes.