[Coda]

If you want to type ディ you type "dexi" or "deli" (both work on Mac, not sure which one is correct on Windows or if both are supported).

It's true that ee and oo are a lot less common than ei and ou because ee and oo don't happen in on'yomi. (I don't know if it's "rarely" or "never".) And since ee and ei both occur in kun'yomi, as well as oo and ou, you have a mixed set in native Japanese words. "nee" (sister) and "too" (as in the number ten) are both native Japanese words instead of Chinese loan sounds. "ooi" (many), "ookii" (large), "tooi" (distant), and "toori" (kinda hard to translate, but "way" among others) are some of the other "oo" words I can think of; I'm not thinking of any other "ee" words at the moment (short of "ee" ("yes") itself) but I know they're there.