Dimitri Vulis
What's important above all is to never create new name translations from thin air.
If Félix is known in sources also with the spelling Felix for sure use both English and Spanish tab as you said.
If not, do NOT invent new translations, put Félix with the accent in the DEFAULT tab only(also known as the english tab), and leave the Spanish tab empty.
Ignore all warnings, conflicts and objections and feel good about yourself.
You did the right thing.
This goes also for umlauts and any other bells and whistles in the latin alphabet.
Let's fight to liberate the default name fields from the oppressive warnings and conflicts.
And also let's fight for better search functionality everywhere on Geni, ie fuzzy search matching. Like how google finds stuff even when you spell things wrong.