vtwm
Virtual twm: twm with a desktop bigger than the screen and a miniature map for getting around it.
It appeared around 1990, alongside tvtwm, and solved the same problem in much the same way: the workspace spanned several screens, and a small Virtual Desktop window showed the whole thing in miniature. Clicking or dragging in the map moved your view. Windows that should follow you everywhere, like a clock or a terminal, could be pinned in place with f.nail.
vtwm also added "doors", little buttons that jumped straight to a fixed spot on the desktop — an early take on named workspaces. Configuration lived in twm's own text format, with the same syntax and the same unhelpful error messages. It has been maintained far longer than anyone expected and still sits in several BSD ports trees, a time capsule with square borders.