High level WC flushing problem

kuepper

I flushed the toilet yesterday and the lever that the chain's attached to didn't return to its position. I could only flush it again by pushing it back up. I thought it was just a matter of tightening the screw that goes through the slot in the side of the cistern but there isn't a deep enough 'notch' on the screw to get a grip with a screwdriver besides which it's awkward to get a spanner on the screw's nut inside the cistern without having a third hand. I wondered if there's something I've missed or is it all down to tightening the screw and if so how do I get it out to replace it with one I can get grip on? It seems like I'll have to get a plumber. I've attached a pic that I hope illustrates the issue