Campagnolo: Can I run an 11 speed chain on my 10 speed chainrings?

Very likely yes this will work fine. The main risks are

• that it is "out of spec" by the manufacturer so a warranty claim might be rejected
• 11 speed chain is narrower than 10 speed so the FD's cage will be a little wider - meaning the shifter has to move a little more to nudge the chain over
• the tolerance changes can increase the risk of a dropped chain on the inside, between, or outside of the chainrings.

Though I've successfully used 9 speed chain on what started as a 5 speed triple chainset, and its still working fine (though its friction shifting which may disguise some shifting issues.)