Issue
In Nintex Workflow for Sharepoint 2016, the link to "Workflow History" is no longer present for "Document Sets", within the item "Edit Control Block" (ECB) menu
Resolution
In order to resolve this, please install the latest Sharepoint Cumulative Update (Post May 2018)
Additional Information
Microsoft had previously made a change to the ECB menu which disallowed modifications to it:
https://social.technet.microsoft.com/Forums/en-US/8c9fa35a-5f7d-4251-a2f2-500ca49f4f72/folder-custom-action-menu-item-in-edit-control-block-not-working-in-sp2016?forum=SP2016
This decision appears to have been reversed in the latest Sharepoint CU
https://social.technet.microsoft.com/Forums/en-US/8c9fa35a-5f7d-4251-a2f2-500ca49f4f72/folder-custom-action-menu-item-in-edit-control-block-not-working-in-sp2016?forum=SP2016
This decision appears to have been reversed in the latest Sharepoint CU