Fuel level 4mm under gasket. That means...

It is about 1/8". That means fuel will be over gasket, when bike is on side stand.

What can I use to cover bowl gasket with?

The gaskets shouldn't need a sealant. If they are old & hard, replace them. If they're in decent shape, you can try soaking them in liquid wrench silicone spray lubricant, let them sit a while, then install. I was able to rejuvenate some old gaskets by soaking overnight --- they were basically the same paper gaskets as the 1000E.

I don't disturb old gaskets. Mine are 20 years old. I use a light coat of grease to help seal them. I did that once two years ago, no leaks. If they're damaged, replace them.
Steve