Comment 4 for bug 180132

So now I got it. You want visitors of yours to be able to use your coccinella on your pc. That didn't come to my mind until now.

So my suggestion is to add an extra tab or something to the login window which lets the user switch to a temporary login form.
Another idea: Install a dropdown menu on top of the login window which lets you choose out of several already-arranged profiles and also includes an item like "new profile for this session only".