We have the ability to lock a complete threat model. This can be viewed at: How to lock a threat model .
Sometimes we may wish to lock individual items to help with diagramming. This can be especially useful on larger diagrams or when multiple users work on the same diagram.
Please note, locking an item like this is not the same as locking the diagram. This is simply used as a tool to assist in diagramming. Changes can still be made at a threat/countermeasure level etc.
Locking an item restricts editing, deleting or moving the object.
Locking a component or trust zone is a simple task.
Start by selecting the item (trust zone, component) you wish to lock.
Ensure the format pane is expanded.
Navigate to the 'arrange' pane.
Lock the item
Once the item has been locked, it cannot be moved, edited or deleted. To unlock the item simply select the item and choose 'Unlock'