There is no Yield Function for it, but if roblox has a plugin (like with the animation editor) then I can use InsertService and copy the generation code.
idk but if you want to make your own custom terrain then
you could make and inviable custom terrain(like 5 of them) and then do:
local terrain = math.random(1,5) if terrain == 1 then game.workspace.terrainone.transparency = 0 end if terrain == 2 then game.workspace.terraintwo.transparency = 0 end if terrain == 3 then game.workspace.terrainthree.transparency = 0 end if terrain == 4 then game.workspace.terrainfour.transparency = 0 end if terrain == 5 then game.workspace.terrainfive.transparency = 0 end