It is possible, but not with the existing Hubitat built-in driver. You can use my Pushover Driver which has had a few enhancements made to it by community members to allow one to choose the tone played on a per message basis by embedding that data into the text message. The Driver then parses that information out and sends the correct request to Pushover.
For testing, you can simply add a new virtual device using this driver, and then copy in your Pushover API key and any other settings you'd like. This will give you a way to test the new functionality without disrupting your current automations/notifications whatsoever.
Note: This driver was the basis for the Hubitat built-in driver. I am not sure what changes Hubitat has made to it over the years. I do know that users are still using my driver without any issues. I just wanted to make sure you were aware.
