The term ‘navel orange’ appears neither in Benson, nor in Wells, nor in Vikivortaro. The English-language version of Wikipedia treats this term in its article on the orange, and there is an offering in the sidebar for the Esperanto-language version, but the Esperanto-language version is merely a stub, and does not deal with this term. Nor is this term in ReVo, nor in Sonja’s English-Esperanto dictionary. So, would the Esperanto translation of “navel orange” simply be “umbilika oranĝo”? – or is there some niftier rendering?
I looked up the translations in some European languages:
French: navel (f) or orange Navel (f)
German: Navel (f) or Navelorange (f)
Spanish: naranja navel (f) or naranja california (f)
Italian: arancio ombelicato (m)
As you can see, most don't translate navel, but instead treat it as a proper noun. It was difficult to find translations for other languages, but I expect there is a similar pattern. It seems that the navel orange is not well-known globally. So I think that you can use either of these:
umbilika oranĝo is a valid translation; however
navel-oranĝo may be easier for a reader to look up and find information about.