Symptoms

In SharePoint 2013, using the K2 for SharePoint app, a user created a workflow for an "appified" list. Nobody other than this user can see this workflow and edit it from the Applications page.
 

Diagnoses

This is expected behavior in 4.6.8.
There is no longer a concept of "reusability" in the K2 for SharePoint 2013 App model. This is because a workflow is tied to a specific appified list/library. So, there is no way to "share" it to use on other lists and libraries, as in the old 2010-mode designer.
 

Resolution

In 4.6.9, we have added the ability for users other than the OWNER of the workflow to see it from the K2 App. This will allow everyone who has permissions to reach the Appify page of a list to see the workflow, thereby giving them access to open and redeploy the workflow.
Since you are still on 4.6.8, then only the owner (person who created the workflow) will be able to see it. Upgrading to 4.6.9 will, however, allow new workflows to be seen by all users with access to the Appify page.