quick and dirty soultion for me to toggle between mac speakers, bluetooth headphones and wired headphones with one keystroke.

better_touch_tools.json

{
  "BTTTriggerClass" : "BTTTriggerTypeKeyboardShortcut",
  "BTTPredefinedActionType" : 172,
  "BTTPredefinedActionName" : "Run Apple Script (blocking)",
  "BTTInlineAppleScript" : "do shell script \"\/php \/Users\/USERNAME\/dev\/togglaudio.php\"",
  "BTTAdditionalConfiguration" : "8519680",
  "BTTEnabled2" : 1,
  "BTTKeyboardShortcutKeyboardType" : 3253,
  "BTTRepeatDelay" : 0,
  "BTTUUID" : "E86A6EE6-0B34-4607-8D94-9AE303AF29CB",
  "BTTTriggerOnDown" : 1,
  "BTTNotesInsteadOfDescription" : 0,
  "BTTLayoutIndependentChar" : "F12",
  "BTTEnabled" : 1,
  "BTTModifierMode" : 0,
  "BTTShortcutKeyCode" : 111,
  "BTTShortcutModifierKeys" : 8519680,
  "BTTOrder" : 1,
  "BTTDisplayOrder" : 0,
  "BTTAutoAdaptToKeyboardLayout" : 0
}

toggle_audio.php

<?php
if (!file_exists("/usr/local/bin/SwitchAudioSource")) {
    die;
}
$as_data_raw = shell_exec("/usr/local/bin/SwitchAudioSource -f json -t output -a 2>&1");
$as_current  = shell_exec("/usr/local/bin/SwitchAudioSource -f json -t output -c 2>&1");
$as_current  = json_decode( $as_current, true );
$as_data_raw = explode("\n", $as_data_raw);

$filter_devices = ["DELL U2720Q"];

$new_audio_output = false;

foreach ($as_data_raw as $key => $row) {
    $json_data = json_decode( $row, true );
    if (is_array($json_data) && !in_array($json_data['name'], $filter_devices)) {
        $json_data['current'] = ($as_current['uid'] == $json_data['uid']);
        $as_data[] = $json_data;
    }
}

$current_key = array_search(true, array_column($as_data, 'current'));
$next_array_key = ($current_key >= max(array_keys($as_data))) ? 0 : $current_key+1;
shell_exec("/usr/local/bin/SwitchAudioSource -f json -u {$as_data[$next_array_key]['uid']}");
shell_exec("/usr/bin/osascript -e 'display notification \"🔊 {$as_data[$next_array_key]['name']}\" with title \"Audioausgang geändert\"'");