You can quickly produce a list of contacts who have left, using a filter:
Click Contacts and then click Filter.
Under Categories column, click Has Left.
Under the Available column, select Yes.
Click the green right arrow (
) to move the field to Selected column.
The list now only shows those contacts who are marked as Has Left.
You can now select those you want to add to a tag file (or tick the Select All box).
Please follow these steps to add the selected records to a tag file.