Hey,
So... the easiest method I can think of would be to use Array Maker. It has an "Array List Contains Name" action.
You can create an array with every audio clip name, and then cycle through them checking which are contained within the Array List (of audio clips) and getting their indexes.
Not a great solution, but that's probably what I would do.
A "Get Audio Clip Name" action would be ideal here, but I couldn't find one.
Maybe requesting it would be the best option:
https://hutonggames.com/playmakerforum/index.php?board=8.0Good luck.