Microsoft is planning to deprecate SharePoint 2013 Workflows. The dates aren't finalized yet, however, Microsoft has introduced new parameter for SharePoint Online to disable creation of new SharePoint 2013 workflows. The existing workflows can continue to run and be modified even after this tenant setting is enabled. This will help organizations to reduce/limit their scope of creating workflows using SP Designer 2013.
Spoiler :) - You must be on 16.0.21610.12000 for Microsoft.Online.SharePoint.PowerShell module.
Step1 : Connect-SPOService
Provide your SharePoint admin URL and SP admin ID/Password to connect to the tenant
Step2: Get-SPOTenant
You should see StopNew2013Workflows as FALSE
Step3: Set-SPOTenant -StopNew2013Workflows $TRUE
This final step will change the status of StopNew2013Workflows to TRUE. Now on your existing SP 2013 workflows will work, can be edited but new workflows cannot be created.
Test Case:
If you try to create a new SP 2013 workflow, while publishing the workflow you should see an error like below.
