How to drag along one axis, despite the camera's angle

I want to duplicate Unity's Scene View Positioning tool. I.e. I have arrows on the sides of an object and when I click and drag them, I want them to move only on that arrows axis.

It only will operate in world space. The camera will not (most of the time) be perpendicular to an axis. I will be doing this for each axis

Is there a script or tool already available? Or does someone know the code for dragging along one axis?

I've seen multiple solutions for this, but those are moving along the screens axis, which is not what I want.