A:Answer The app JBL recommended to you only does one thing: shows you a battery bar. But your Flip 5 already has that.
There is literally nothing else the app does for your speaker. No equalizer, not even general bass/treble, no volume control, no power, no nothing.
Well, it does tell you if you have the latest firmware. But I've had my speaker for well over a year, and the firmware it came with is still the latest version.
If you're looking for a speaker that the manufacturer cares enough about to create an app that actually lets you control the speaker and customize the sound, the JBL Flip 5 definitely is not it.