Is there a way to attach two email signatures in FYI?

You can only display a single email signature at a time. 

This can be either:

• The default Email Signature selected in the Practice Settings.
• The Email Signature selected in the User Profile (overriding the default practice signature). 

 Refer to Creating Email Templates and Signatures.

As an alternative, consider adding content to your templates instead, or sending the draft to Outlook and utilising the Outlook signature functionality.