I have another stunning idea. I call it Hovel Carving.
Wiki style entry:
In-Game Text
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Hovel Carving
"Now y'see son, not all cavemen are primitive."
Hovel Carving allows you to erect artificial cave entrances and also to mine and seal cave walls.
What it Gives
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Adventure > Cavescaping > Carve Cave Wall (only for natural caves, use Mine for artificial ones)
Adventure > Cavescaping > Seal Cave Wall (natural caves only)
Adventure > Cavescaping > Build Cave Home Door (new cave to modify)
(everything from here down is artificial cave only)
ability to right-click cave wall and click "Seal"
Adventure > Cavescaping > Build Rock Shelf
(carves out a 4x4 hole in the wall, requires 5 rock wall in a T pattern and the upper part of the T being the shelf's opening)
Adventure > Cavescaping > Build Rock Chair
(same as normal wood chair basically)
Adventure > Cavescaping > Build Rock Cauldron
(clay cauldron like cauldron)