I tried searching on this and ironically found a thread in my previous device's forum (HTC Desire) from 2010, describing exactly the same restriction. Which means I don't hold out much hope
I did wonder whether a third party contacts app might offer it, but couldn't find one which mentioned the feature. I tried one, but it just used the standard contact adding dialogue - which TBH is what I'd have done to maintain compatibility. So while there might be something out there, I've not been able to find it so far.