In Workflow 8.1 model can no longer be dragged from project sub-window to automatically create a Linked Model configured to the model you dragged from.

This behaviour has changed from earlier versions of Workflow and makes life a bit more inconvenient.

The simple workaround is to add a Linked Model component manually and configure it to the appropriate model.

This behaviour has been reverted to the original - model can be dragged from project sub-window to automatically create linked model - in Workflow/ServiceDesk 8.5.