A flavour board is a list of decisions, and most of them are legible from the outside. The single most useful question at any counter is not what is in a scoop but what the second ingredient is for. There are only four honest answers, and a pairing that cannot give one of them is there to be photographed.
One: it sharpens
Salt and acid both do this. They do not add flavour of their own so much as make the first ingredient taste more like itself, by cutting through sweetness and resetting the palate between spoonfuls. Salted caramel is the famous case; olive oil with sea salt and strawberry with black pepper are the same mechanism applied further out.
Two: it lengthens
Fat carries flavour compounds and holds them on the tongue, so adding fat makes a flavour last rather than making it louder. Olive oil, nut pastes, egg yolk and cream all do this. It is why a lean fruit sorbet tastes bright and brief while the same fruit in a dairy base tastes rounder and stays longer.
Three: it counterweights
Bitterness against sweetness, and the reason a serious board always carries a bitter chocolate or an espresso. Cacao nib, burnt caramel, amaro and strong tea all pull in this direction. A board with no bitter entry anywhere is a board that has decided not to challenge anybody.
Four: it adds texture, not taste
Chocolate shards, crushed wafer, candied nuts, biscuit. These change the experience without changing the flavour, and they are the most honest kind of addition because nobody pretends otherwise. Granizado is the Argentine version, covered on the Argentine helado page.