Hello Ellie,
This Tag and those comments are for the Transmission (default) provider Tags at the Edge and not for Engine Tags. You can add additional Tags and Folders for publishing at this ‘default’ provider at the Edge Gateway.
As you noted, published MQTT Tags are written into the MQTT Engine managed Tag provider while using our MQTT Engine module. This is where MQTT and MQTT Sparkplug messages will arrive from your MQTTx Client (through your MQTT Server) if the Engine User is subscribed to the proper Topics as controlled by your Server.
But you cannot manually add any Tags in this managed Tag Provider. However, you can create Gateway scripts on any Tags in that Provider to publish an MQTT message.
By default Engine can be configured to write back to any Transmission Sparkplug Tags (shown) that arrive in the Edge Nodes folder as these are Sparkplug formatted which is the formatted payload Engine will produce in that command message. Your example shows those to be MQTT Transmission module Tags.
But if the incoming Tags are not Sparkplug Tags but are instead MQTT Tags then you must script a reply using the Gateway Event scripts tools. See these examples in the tutorial below.
https://docs.chariot.io/display/CLD80/MQTT+Publishing+via+MQTT+Engine
Something else to consider is that there may also be some ACL or other changes required at your MQTTx Server for the Engine user to publish messages through that Server.
When using our Server products (MQTT Distributor or Chariot) there are no changes required for the default Users for MQTT messages publishing or subscribing from any MQTT Clients.
Regards,
Daniel