There's a release era trick that still works, it's manual but gets the job done. When you scrap anything in the build area, the bar lowers. Drop all those junk pipe rifles and such and scrap them. You can even dump things like actual scrapped resource piles (steel, screws, aluminum, etc) and they still count. Not as much but still. Items that have larger polygon counts and meshes give more space, so the little 'boxes' of gears and such don't give much at all, scrapping finished items gives a lot more. A friend setup a basic builder line making teddy bears, dropping them into a walled room, then went in and scrapped them. Loses 1 leather 1 cloth in the build/scrap cycle.