Disable MQTT Transmission to see the tags go stale in MQTT Engine
Set the 'Primary Host ID'. This is a setting that is highly recommended and should be set on both MQTT Engine and any MQTT Transmission instances that are reporting in as well. Video 10: Primary Host ID Setting: Implementing MQTT in Ignition
Set up Store-and-Forward in MQTT Transmission to show data being saved when the connection goes down. Video 12: Set Up Store-and-Forward System: Implementing MQTT in Ignition
Load and configure a database on the primary ignition gateway and then associate Tag History using Ignition Designer Tag Historian in Ignition
Use a Custom Transmitter rather than the Default Transmitter to provide more flexibility on the MQTT Transmission side in terms of tag tree/arrangement MQTT Transmission Transmitters and Tag Trees
Add additional MQTT Transmission modules pointed at the single MQTT Distributor instance set up in this tutorial