Hi raymond.
Thank you very much for your suggestion. It works! With the correct entity % 😉
But by checking this I found a bug:
When you click on the button from an existing shortcode to edit it, the plugin does not only load the existing code. Even in html view it decodes entities! This is not only relevant for users like me, who want to „trick“ the plugin to work with „%“ in the shortcode.
No, as you can see above in the code (in my first posting you can see the original code), also the „&“ in the url are encoded („&“), because the url is a parameter from „http://w.soundcloud.com/player/?“.
Therefore you cannot edit existing shortcodes easily. When you do not save the shortcode anywhere else, you have to search for it in the mysql database. Or even re-encode the shortcode.