Nintex Workflow (2010 & 2013).
The "Workflow Inventory" feature was released in January of 2016 in version 22.214.171.124 of Nintex Workflow 2010 and version 126.96.36.199 of Nintex Workflow 2013:
January 2016 Nintex released a new feature to help workflow admins see exactly what's going on with Nintex Workflows with the introduction of Workflow Inventory. You will need the appropriate administration access to access the different views.
All previous legacy versions do not contain the Workflow inventory feature. And they will not even see the option to view the workflow inventory page.
Customer running these legacy versions will need to update to the above version depending on their version of Nintex workflow.
Workflow Inventory is a Site Setting area which will lay out in detail all the List and Site Workflows published to that Site, all sites in a Site Collection or all Sites in the Farm; providing in an easy to understand list.