It used to just be active when adjusting or drawing a new node and holding SHIFT to constrain the direction.
Now you have to hold the SHIFT button to constrain your movement and then press 'Q' to activate the tool.
Barry.
One of the forum moderators.
Versions 6.5 to 27
i7-10700 @ 2.9Ghz, 32GB ram, GeForce RTX 2060 (6GB), Windows 10
Lenovo Thinkpad - i7-1270P 2.20 GHz, 32GB RAM, Nvidia T550, Windows 11