Shortcuts on iPhone: Get file action

Hello! The goal is to create a shortcut which shall play a specific sound file upon a specific action. To do that I use the "Get file" action and iCloud as source. By default it would come up with a file picker. When switching that off, it expects the sound file in path iCloud\Shortcuts.

The problem is that the File app is unable to copy or move any file into that folder. The existing shortcuts shared across my devices via iCloud are not even in this folder. The folder is empty. As a side question I wonder what this folder is for.

Main question: How to use the Get file action this way if I can't use that folder as source?

Alternative gone wrong: there is the option to encode a sound file to Base64 and use it together with "Play sound" action. After encoding and copying/pasting the data into the action it would still not play my sound file, like there was no Base64 data at all. It would just play that standard sound.