WARNING: DO NOT START A NEW GAME WHEN THIS MOD IS INSTALLED!

Some settlements have small interior cells in them or nearby. This mod places a workbench and a power source in them.
The new workbenches are all linked to the main settlement workbench. Usually, they require you to unlock the main workbench first.

I tried to make some of the statics at least theoretically scrapable, but you will probably still need something like Scrap Everything or Place Everywhere, which would actually allow you to scrap the trash in there.

Warnings:
Only install the mods for settlements you unlocked already. I can't guarantee that it will work otherwise. It's perfectly fine to install only Sanctuary at first, then, after unlocking Croup Manor, select "reinstall" in your mod manager and select both Sanctuary and Croup Manor.

Place the files low in the load order. Turns out, a lot of other mods also touch these locations. Usually just to place a few new items there. The files from this mod must absolutely be placed BELOW such mods, or it will cause a conflict.
Symptoms of a conflict can be affected settlements appearing twice in the "Send settler to" list. If you have SimSettlements, Visitors might also appear in the interior cells in case of a conflict.

If you are using NMM, you might not be able to move these files down in the load order. You really should switch to MO2 or Vortex. If you want to stay at NMM, use this mod, and have conflicts, use xEdit to fix this manually.


Affected settlements:

Croup Manor:
The flooded basement. The workbench is the toolkit on the shelf oppostite of the entrance. The power connector is above the terminal. A water valve on the pipes opposite of the terminal can be used to remove the water.

The Castle:
The tunnels. The workbench is next to Sarge. The fusion reactor now has a connector on top. Here, the workbench also requires you to get the artillery blueprints first.

Sanctuary:
The root cellar. Has a toolkit workbench and a connector in one of these connectors on the ceiling. A little hard to use, though.

Bunker Hill:
This basement which you can only enter at Battle for Bunker Hill. The workbench and fusebox are in the metal walkway. There is also a radio beacon in the room at the end, which can be used to get rid of the NPCs and turrets left over from the quest.