The "Gate valve" subflow operates in one of two states: pass- or blocking. In pass state every input message is passed unmodified, in blocking state incoming messages are not passed thru.
state is set via control messages. control messages are input messages
with payloads of either
{"pass": true}
or {"pass": false}
.
control messages are never passed thru.
messages are passed unmodified or not at all, depending on state.
Copy flow.json to your clipboard and then import into Node-RED using the Import From > Clipboard (Ctrl-I) menu option
Is there a sample flow for those of us who are JSON-challenged?