Finally, in principle you should be able to add these junctions/magnets by CMD-clicking at new points on the line.

Good enough for approximate work, but for some reason it seems to generate slight horizontal inaccuracies on my system … (holding down the SHIFT key should reduce them)

(If you select a magnet node, and kept the SHIFT key down, you should be able to drag the node to a new vertical position without introducing a kink into the line)

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