Maple Coco- not sure how I feel about Maple. nms
Indigo Posy- love this
Indigo Maple- cute. If you want to use Maple, I think I prefer it as a mn
Indigo Coco- cute
Prestyn Harper- not a fan. The only Prestons I know are male.
Coco Maple- Prefer this to Maple Coco
Haven Coco- cute
Milo Clover- not a fan of Milo as a name for a girl, but I like Clover
Harper Coco- Prefer this to combo to Haven Coco
Maple Coco - Maple and Coco are both very cutesy, girlish names. Maple has started to grow on me, but Coco is a little silly. Maple Coco/Cocoa sounds like a breakfast cereal. Maybe Coco as a short form for a formal middle name? Colette, Cosette, Cora (Coralie, Coraline), etc., could work.
Indigo Posy - Pretty, but sounds like you're describing something; it's like naming your kid Purple Flower. But I love Indigo nn Indie. Posy feels a little nicknamey; how about Poesy spelling? Has that lovely floral sound, and also is a word meaning the composition of poetry. Posy and posey are slang words meaning a person who acts in an affected way to impress others; i.e., pretentious people.
Indigo Maple - Tad too naturey....
Indigo Coco - Like Indigo, you know my feelings on Coco from above. Also, they don't flow well, too much of the "oh" sound...in-dig-oh, coh-coh...
Prestyn Harper - I beg of you, use the Preston spelling if you use this name. As a separate note, I happen to really dislike the name Preston, and have only heard it on boys, but Prestyn is absolutely abhorrent. Harper is another unisex name, so Preston Harper isn't a great combo. Harper is fine, if very popular.
Coco Maple - Again, sounds like a Kellogg's product.
Haven Coco - Haven is too trendy; doesn't fit with Coco.
Milo Clover - Milo is a boys' name. Mila is not. Clover is okay, makes me think of cloven hooves. Prefer Mila Clove.
Harper Coco - Harper is okay, prefer Piper.
My favorites: Indigo Poesy, Mila Clove, Maple Colette, Maple Cosette.
Maple Coco -- This sounds like a flavor to me -- maple and cocoa together -- and not an appealing flavor at that.
Of all your names, I like Clover best, and I would love to see it in the first place. I also like Indigo, and think Indie a darling nickname. This is my second choice for first place.
After that is gets more complicated. You have some whimsical choices, and there is nothing wrong with a little whimsy -- it can be a valuable ingredient in a name, making it light and airy. But for me, there is a line you don't want to cross with a whimsical name or it floats off into absurd. This makes pairing your choices difficult for me. I am also struggling because so many of your names are two syllables. Do you like any one or three syllable names for the second place? Also, because so many of your choices are whimsical, you might want to pair with something more traditional. For me this just highlights the adorably offbeat choice -- something like Clover Victoria or Indigo Fay.
Good luck. I know you pick something unusual.