Nice one, I'll note that down. I'm pretty sure placement doesn't matter, but I'll put it with the rest of the biome/site data because that's where people will look for it.
For candy, what I'd do is add a candy material(s) to the plants. Then you could take dwarven sugar/syrup and maybe some other ingredients to make things like candied apples(or candied plump helmets). For hard candies(I'll call them sweets because I'm English and Dorf Fort tends to go for the old fashioned terms anyway), there'd be a way to make an extract from the plants and then mix that with sugar/syrup for a slightly more valuable sweet that's essentially hardened sugar flavoured with that extract. Marshmallows are basically sugar held together with gelatin, IIRC, so I could just add a marshmallow material that's made from cartilage and sugar. Hmm, looking at Wikipedia, they were traditionally made from the marshmallow plant, and softer ones can be made using egg whites or agar. Wheat worms might be usable as marshmallow base(anybody want to try this at home?). I'll see which plants I think might be good for making mallows from, rather than just flavouring or colouring them. Candy canes I'll probably handle by requiring to kinds of dye, rather than two flavours, since they're going to be derivatives of the flavour plant.
Another idea is bread and cakes. Take flour, mix it with some kind of booze for fluid and as a raising agent(since we don't have baking soda), and make the resulting batter [EDIBLE_WHEN_COOKED]. And edible raw if it's a sweet version using eggs and sugar or mead. Ponies can then use this in cooking, since they're already making cupcakes, pies, muffins and baked bads. We'll assume the dough in big tasty stews is made into dumplings.
Here's my current list of bugs and plans for the next version:
Bugs:
wood wood bug: conjured woods have wood at the end of their names, this is wrong and makes ponies have preferences for (colour) painted conjured (plant) wood wood.
apple slices: green apple slices are just called apple slices.
Prefstrings: Ent prefstrings not displaying right now. May be due to having caste-level descriptions, I've seen ponies that like green apple ents for their .
[BUILDS_OUTDOOR_FORTIFICATIONS] needed for civs to expand.
Adjust dye plant biomes to combat farming issues, maybe by switching to [BENIGN] and [SAVAGE] tags.
Planned for next time:
Fix Diamond Dogs
Add Griffons as a civ. Maybe change creature_fanciful griffons to gryphons for giggles.
Add more ents: lemon, lime, orange, laraha, banana, plantain, ensete, pear.
Painted leather: Add various painted leathers, reactions for that, and add them to standard materials.
Cocktails, candied plants, sweets, dough(savoury and sweet) as derivatives of various plants.
Marshmallows as animal and plant derivatives. Separate reactions for cartilage, hide, bones and skulls. Hoofs and horns are keratin so they're useless.
That's a lot of very fiddly stuff and none of the bugs are too serious, so feel free to settle in, this'll take a while.
I might make a challenge version with various surface-dwelling animal pony civs to harass the player. Another possible solution is to add more megabeasts, or maybe hemi-semi-megabeasts creature that are just big, ubiquitous and predatory, with a small population, so that wherever you embark, you could be attacked by something nasty long before megabeasts show up. These'd definitely be additional modules, so don't worry. And anyway, it may be an easy beginning, but you're going to be besieged by diomedian ponies later.