Versions
SharePoint 2010, 2013 and 2016.
On-Premises to On-Premises migrations only.
Symptoms
You want to view the Nintex Workflows associated to an item, but when you select Workflows, you only see your Sharepoint Workflows (if applicable).
Solution
To view you Nintex Workflows:
Click the dropdown next to the item.
Select View Workflow History.
Details
Sharepoint will only preserve the workflow information for SharePoint workflows. However the execution history on Nintex workflows is logged, so you can see them when you click on View Workflow History.