You can do, but I never did it. For me the best thing of using Nitrox is getting some safety margin when diving at the edge of NDL, at depths between 25 and 34m (which is indeed a quite rare case, at least for me). In such situation, I prefer to leave the Leonardo set to Air, so I benefit of some additional safety margin.
If you set it to Nitrox-32 (which is done in just 4 keystrokes), you loose the safety margin (gaining some more bottom time, which I do not really need).
Not to be over critical ,,,, you dont loose your safety margine by running in ean mode. in air 1100 ft ndl would be 20 min in ean perhaps 25. you gain mn nothing by staying in air mode. the difference is that if you stay to 21 minutes in air you are in deco and in ean you are still ok because of the remaining 4 minutes acting as your buffer. those that dive ean in air mode is tricking the system in to a false security. yea it insures you stay further away from the real ndl. but the SI times being used no matter what will be calculated based on air. the problem is you really do not know what your condition is because it is calculating a dive that is not happening. if you stay a bit too long you have to do deco and if you skip it because you know you really dont have to do the stop because you have a safer ndl gas (EAN) you are breathing you end up locking out your computer and you are SOL for 24 hours. Every cheat has a cost. IMO you should dive with the correct gas in it and only dive to say 3/4 of the provided ndl. That will give you the same exposure buffer you want but the SI off gassing calculations for residual nitrogen will now provide more accurate data. The idea of diving EAN and using a computer in air mode was the concept of your computer was not a nitrox computer. using a non nitrox computer and breathing nitrox would not cause a risk factor because the air mode is more conservative all the way around. In short diving in air mode was a work around for not having the right equipment. If by chance you went to a chamber they will look at your puter to see what you did and they will now assume you were breathing air and not another gas.