Though you can create a new order, it doesn't work with some billing calculators, esp. those that need the details from the 'checkout' view such as card number, etc... so it probably only works with the 'Bill Me' calculator set as the default at this time.
FYI,the pass thru calculator allows some of this support, but not a full implementation if 'capturing' transactions is not typically done outside of Exponent.
Though you can create a new order, it doesn't work with some billing calculators, esp. those that need the details from the 'checkout' view such as card number, etc... so it probably only works with the 'Bill Me' calculator set as the default at this time.