Backend Workflow to send email to multiple users parameter option is empty

I am trying to create a backend workflow to send email to multiple users and everything logic wise is fine but when I try and add the “to” field on a list of users workflow, the option for “This User” doesn’t show up and I can’t trigger the backend workflow. I have the backend workflow set up properly so I am lost. Any help would be appreciated. -Bob

Trigger

Backend Workflow