Hi @StevenR20. When a file of contacts is uploaded, you will select the list(s) the file they will belong to.
If you have a master list but know that not all the contacts will belong to the same list, you can import the contact tags (for example Dogs, Cats, Birds). Once the file is uploaded, you can search by tag, select the group of contacts with the same tag (ex Cats) and create a new list from the tagged contacts
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