The best thing to do is search Remote central for the codes.

Then Import the HEX codes into Nevo.

This will work 100% as it has no affect on database codes.
Also, don't forget you can use the "Advanced Keys" button to get more codes. This will work for codes that you found using the online search.

Start with a basic set of codes, say T0556.
Use the advanced keys to find as many database codes as you can.
Now press the yellow pencil (to the right of the device name in your device list) and add the missing commands via HEX.

D.