OP am I right in guessing your custom preparing a world prior to play with Buddies? If so then the Upgrade_World by JereKuusela MOD is your friend here.

What i did was explore the world, Build some bases/quest areas.
run this mod to blank and re roll stuff like tar pits/caves etc
Hide the map again then uninstall the mod
The resultant db of the world has my prepared areas still but the fine details are still random so I still get some surprises when exploring .

That mod I feel ought to be in everyone's library (I access via thunderstore mod manager) as it allows excising worlds to get the new content without loosing builds without needing to run a fully modded server.

OFC if I'm wrong in my guess do tell! What have you got planned you have me intrigued!