The widget doesn't work as expected on multiple value field

I tried testing this patch on empty installations of Drupal 9.5.7 and 10.1.x-dev and neither works successfully in the default Claro theme.

The default multiple-file-upload UI in D9 & D10 uses an upload widget and then adds the uploaded files to a sortable table:

When the Audio Recorder widget is used in D10 instead of the default file widget the first audio file is recorded, but it is never shifted to a sortable table and there is not a mechanism to add a second recording:

This behavior is the same as without this patch in D10.

In D9 in contrast, the first recording is saved and then the UI dissapears and a second recording can be made, but there is no indication of the first recording existing:

Without this patch in D9 the behavior is that the single file is recorded and then left in place with no option to add another (similar to the D10 state with or without this patch).

I haven't dived into the default File widget to understand how it works and which parts would be good to override or re-implement in the audio-recorder widget to get a similar behavior with multiple recordings with just the actual upload part (and file link-vs-audio-player) replaced.

In addition to other possible changes, it is likely that FileWidget::formMultipleElements() and FileWidget::processMultiple() will need to be overridden to support recording multiple audio files.