After successfully checking out a subset, click 'Diagrams' -> 'Action Diagrams', there are not any 'Procedure Steps' in the list. The same Procedure Steps display correctly in another model, it can be displayed in Action Diagrams.
Release : 8.5
Component : CA Gen Workstation Toolset
The reason why procedure is not showing in the list of Action Diagrams, is because the correct Business System must be selected first. Go to Business System Defaults and select the correct Business System, highlight it and Open it . Now the Procedure Steps can be seen in Action Diagram list.