I would like lines on my project to snap to the red rectangle’s axes, rather than the world axes.
Hi,
Set your topview cplane to the desired rotation of true north.
Make sure universal cplanes is turned off in Options/modeling aids.
Use cplane 3 point command and orient your new cplane to the axis of true north via that selected rectangle in your image.
You can even open this in a new top view, viewport if you wish and save the cplane as true north.
Hopefully your displayed line work already follows that orientation or else you might run into drawing problems with two different orientations.
RM