If you choose the angled geometry method, you can choose the angle from the first two points you click when placing the dimension.
This may not help in your situation if you want the dimension angled but still square to the elements.
You can use intersecting guide lines to get the points you want but the dimension will not be associated.
Or you can temporarily rotate the plan so it appears square (orientation angle at the bottom of the plan window), then dimension, and then set back to 0°.
Or just adjust the dimension you have placed.
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