- Left-click to place a single belt and hold the mouse button down
- Press M to open the map (keep the mouse button held)
- Move the mouse a few tiles in the direction of the belt
- Press M to close the map, then release the mouse button
Expected result: Not sure. Expecting to build with the map open isn't really reasonable, so either cancelling the build or continuing to build straight segments of belt seems ok. Building an underground is strange though.