Okay, those are virtual pins in Blynk speak.
Take a look at this…
The last option (Node-Red) is what I use for my home automation projects, but it might be an overkill for what you want, but if you need two-way communication between a master and three/four slaves then you’ll need each device to be a device from Blynk’s point of view, and therefore will need to upgrade to a better subscription plan.
These devices will also appear in the app, but would need to be ignored (you wouldn’t create dashboards for them, but the devices would still be there).
With Node-Red Blynk only sees one device and you can have multiple slaves (I have around 25 devices, but only one device from Blynk’s point of view).
Pete.