Enable SPD2013 workflow with content type association
SP2010 + SPD2010 allows to define a reusable workflow on content type level. This enables to utilize CT specific fields in the wf actions + conditions. As of SP2013 it is not possible to assocate to Content Type in SPD, and not intuitive to select in designer the CT specific fields. This complicates the definition of business workflows by SharePoint business/power users.
This workaround isn't stable. I recently tried this and it won't save the content type, even trying to follow the links in the comments. It needs to be a simple selection in the workflow settings screen.
Marc Nemegeer commented
I believed you, until I stumbled upon https://blog.lekman.com/2015/02/creating-sharepoint-designer-reusable.html. This article shows to define a 2013 workflow for a content type ;-) The same is explained on TechNet http://social.technet.microsoft.com/wiki/contents/articles/33157.sharepoint-2013-create-reusable-workflow-on-content-type-using-sharepoint-designer-2013.aspx