Clean up ugly tangles of copper wires with an area selection tool. Use the quickbar shortcut or the hotkey (default Alt+E) to get a cleaner tool in your cursor. Has three modes:

Left mouse button: remove unnecessary diagonal wires.
Shift + left mouse button: remove all unnecessary wires (diagonal first, then vertical, then horizontal).
Right mouse button: add wires, where possible, in an orthogonal grid between poles of exactly the same type.

There is also an undo hotkey (default Ctrl+Alt+E) which will revert the last action made with the cleaner tool, but only the last.

Wire removal uses Tarjan's bridge-finding algorithm to ensure that electric networks are never split (i.e. a wire is "necessary" if its removal would split a network). However, adding wires can merge networks.

Wires to poles outside of the selected area are never added or removed. Circuit wires are ignored. Not intended for massive area use - the algorithm is quite efficient but the tool will refuse to work with selections of more than 300 poles.

Inspired by, but not based on, Power Grid Comb by shanemadden, which is a fine mod but I wanted something that worked a little differently.