Thread:Project:Support desk/How to add custom buttons to WikiEditor?

Manual:Custom edit buttons only works with upload.wikimedia.org URLs?! As soon as I use my own URL I get

Uncaught TypeError: undefined is not a functionload.php?debug=false&lang=en&modules=site&only=scripts&skin=vector&*:1 (anonymous function)load.php?debug=false&lang=en&modules=jquery%2Cmediawiki&only=scripts&skin=vector&version=20150103T1…:44 jQuery.Callbacks.fireload.php?debug=false&lang=en&modules=jquery%2Cmediawiki&only=scripts&skin=vector&version=20150103T1…:45 jQuery.Callbacks.self.addload.php?debug=false&lang=en&modules=jquery%2Cmediawiki&only=scripts&skin=vector&version=20150103T1…:48 jQuery.fn.readyload.php?debug=false&lang=en&modules=site&only=scripts&skin=vector&*:1 (anonymous function)