Whilst researching the MQTT topic I discovered a simple client available in the Windows Store, for those wanting a quick, easy, Windows orientated way to look at MQTT this might meet your requirement.
I would recommend to test MQTT Observer at GitHub. It was created as an helper in an Escape Room 2.0 project to monitor several Arduinos and Raspberries.
You create observation displays to filter out some topics, to filter out some messages starting with specific strings and to display fool topic or extracted correspondent. You can identify forgotten topics with remaining wills, and select wills to reset.
Save server and observation settings as sessions, to retrieve further.