By default all diagrams are read-only. To change or update a diagram it is necessary to click Check Out on the Home tab. This will enable you to perform any changes on the diagram, and for everyone else, the diagram will be locked.
Doing so avoid inconsistencies, as single-user editing prohibits conflicting updates on shared data, which is important to maintain integrity. However, you may override this feature by forcing an unlock at which point Bizagi Modeler will warn you that conflicts may occur.
A locked diagram is evident by a display message stating that the model is read only.
Click the username link.
A window will display showing the users currently editing the model.
If you click the Unlock diagram button the following warning message will be shown.
Click the Yes button. This will unlock the diagram and you will be able to make the necessary changes.