Recently I was trying to add vines to the crag biome, and doing it with flora was the logical way but it had a minor issue that made it a bit infuriating, the vines weren't going up to the very top of the moutains like so :

and I had to make a terrascript to have the wines that I wanted, but it could be still possible to do with flora with a little adjustement

The feature

it would a path in the flora config adjacent: that could look like so

adjacent:
  - top:
    - "minecraft:stone"
  - left:
    - "minecraft:sand"
   ...

it would spawn blocks next to where the flora is supposed to be spawned (and would only replace air ?)

maybe having something more flexible like :

adjacent:
  - 0, 0, 1:
    - "minecraft:stone"
  - 1, 0, 0:
    - "minecraft:sand"
   ...

where 1, 0, 0: would be the offset from the initial position

Thanks you for reading, I hope that my explanations are clear enough :)

Flora objects are, per our definition, vertical only. If you want to place blocks adjacent to flora, use scripts. Your description of what you want "adjacent" to do was very cryptic, but it sounds like you want it to place blocks around the flora object, but correct me if I'm wrong.

Plus, would this not do what you want?

ceiling: true
search: DOWN
spawnable:
  - "minecraft:air"
replaceable:
  - "minecraft:air"
rotatable:
  - "minecraft:stone"
  - "minecraft:cobblestone"
  - "minecraft:mossy_cobblestone"
irrigable-offset: -1
irrigable:
  - "minecraft:stone"
  - "minecraft:cobblestone"
  - "minecraft:mossy_cobblestone"

Any update on this? I still don't understand what exactly this is requesting...

I'm going to consider this stale, since I still don't know what this is requesting, and it seems like the original issue can easily be solved with existing options. Feel free to reopen if I am mistaken, though.