As I understand it, the MQTT data you see on the panel is ephemeral. If you want to go back and view the dataset at a prior time, I think you would need to have the data in time series database (like InfluxDB). Besides the MQTT datasource plug in, have you created any other datasources? It would not be too difficult to set up a routine / program whereby the data is streamed via MQTT and stored into the database.
