If you have delegated to Workiva, you do not need to provide a Filer API Token so having a backup token isn’t strictly necessary.  You can create as many Filer API Tokens as you desire in the EDGAR Next Filer Management dashboard, although one quirk is that once created, you have one opportunity to copy or download the token, then it is still active but you can’t re-download it.  Workiva will provide functionality for you to upload one or more Filer API Tokens into your account, so if you want complete redundancy, you could create a new token every 6-9 months, upload it into Workiva, and always have a secure storage location for the tokens.