Changing slideshow speed during a slideshow?

After having started a slideshow (fullscreen), the only way to adjust the speed of the slideshow seems to be to open the preferences from within DOpus. Right-clicking into the slideshow window allows saving, printing, converting, copying, moving and deleting the file etc., but there's no option for regulating the slideshow speed. Or did I miss something?

Well, I could end the fullscreen view and click on the preferences button. But if the image that is displayed is for example a RAW file (and the RAW plugin is installed), this button brings me to the plugin settings instead of the DOpus preferences.

It would be nice if there could be a right-click option to adjust the slideshow speed, and it would be perfect if I could also choose if the new speed should be set permanently or just for the current slideshow session.