On the 2014 A6 you just hold the right paddle down and it will return to drive in a couple seconds (if the shifter is in D of course). I assume the A8 is the same.With only 100 miles on the A8 I haven't attempted anything out the ordinary. Not sure of the even or odd gear selection. I must say I'm impressed on both the D and M selections. Smooth but firm shifting without going nuts in D. In the M mode those paddles give this car a real tight feel. Until I get over the break in miles, I cannot comment on the shift timing under load. Interesting find, if you are in D the paddles are still active. Meaning the transmission switches into M and provides visual indication of which gear you are in. NICE ! You can be driving down the road in D, touch either the + or - paddle and the car drills down to the selected gear and the indication on the 'shifter' goes from D to M. Still working on how to go back to D but what a nice feature. Also there is enough smarts with this car that as you downshift in M with your foot off of the pedal it automatically compensates the engine rpm as to not jerk you forward. Again, nice. Still experimenting but thus far I'm having fun with the A8.
It will go back to D on its own if you arent doing what the computer thinks is 'performance' driving as well.