I just saw it written on the squadroom board as “Amengual.” Unless the spelling changed later in the show, there’s no reason to spell it otherwise. And with Chano being Puerto Rican, the name would not end in a silent E. (BTW, while “Amengual” is not an actual surname in Puerto Rico, “Mangual” is—it originated in Catalan-speaking Mallorca in the Balearic Islands off Spain’s Mediterranean coast, and was alternatively spelled “Mengual” in the old country.)
IMDb also has it spelled as “Amenguale.” The spelling on the wall assignment board might be in error. His deskplate (which he should have) should settle how it is spelled. I can’t remember if it was spelled with or without the “e.”