Hi Isabelle - That's a toughy! Here are some thoughts:

• I would probably change my bathroom habits so I never set anything on the right side of the sink. Just act like it's not even there. Maybe as a reward for that habit, have a little plant that would enjoy the window on that side. (In a bottom-heavy container you won't knock into the gap!)
• Maybe get some kind of countertop cubbie with openings on the top that's big enough not to get knocked off. Then you'd be reaching down into it to store anything. Anything big enough not to get knocked off will look a little awkward, though, crowding up next to the sink.
• Is there any way to create more surface or storage space on the left side of the sink or below the mirror? That might decrease the need for the things to sit on the right side of the sink.

Hopefully something there helps! Best of luck.

Doug

Is the heating vent electric or hot water?