How do I reference a Field from the SharePoint 2013 List that I created for a new Nintex Form/Workflow, that is not already predefined in the "Common," "Item Properties," or "Inline Functions?"
I believe you are talking about list workflow and you have added additional column onto the same list which has the workflow? Correct?
Generally you would see all the columns in the list in the Item Properties section. Was there a specific way you created this new field? What is the data type of this new field you have created?