A flow in the Flows pane can be locked for editing.
When a flow is locked, the Flows pane shows the 
state icon when the flow is inactive and no changes can be
made to the flow design or to the flow's properties. The flow can still be activated as
usual. The icon is not visible when you activate the flow but the flow remains
locked.
Locking status is preserved when the flow is exported and re-imported.