Third-Party App Notification Sounds

I use a 3rd Party app called Tiimo to help me manage, well my life basically, but especially executive functioning, because I’m on the Autism Spectrum. So this app gives me alerts all throughout the day & the sound notifications are very helpful. But the default 3rd Party App notification sound is so very jarring, to the point of undoing some of the benefits of the app. Is there a way to change the notification sound for 3rd Party Apps?

And I don’t mean customize it for each app, just change the sound all 3rd Party Apps use. Most 3rd Party Apps I turn the sound notifications off, because they’re unnecessary & jarring, but this app is the one exception where it’s pretty necessary.