Extending Craft Commerce admin templates I would like to add an option to the gear menu seen below in Craft Commerce, is it possible to extend those templates ?

The idea is to create a plugin to export the selected orders to a CSV file
It's not documented on the Commerce site (yet), but Commerce does have commerce_addProductActions and commerce_addOrderActions hooks that a plugin could latch onto to add its own custom actions to the Order and Product index pages.

Virtually identical to the add(Element)Actions hooks that Craft provides for its elements.