I don't think so - have a look at the CSInterface.js source for confirmation.
I can [nearly] confirm what Davide said. Here is a link to the latest CEP: https://github.com/Adobe-CEP/CEP-Resources/blob/master/CEP_6.x/CSInterface.js
Refer to Line 1095. Docking interrupts the existing re-sizing feature. Given that, I don't see any way that you could even begin to programmatically dock an extension. I have some good experience with CEP and have never heard of such a feature.
Of course, none of us really know without word from Adobe itself, but I would seriously doubt the function you are asking about exists.