A flow can be in different states:
An inactive flow is in "design mode": the flow can be changed at will and flow element properties can be updated. An inactive flow can not process jobs.
An active flow is currently being executed by Switch server, that is, it is processing jobs. An active flow cannot be edited. This state is indicated by the
icon next to the flow name in the Flows pane, and by the darkened background in
the canvas.
See flow states for more information.