Hi Max, for the next v3 beta I've implemented a shift "Straight snap enhancer" which I think will do what you want.

The way it works is if you have a straight snap currently active, you can then hold down shift and that current straight snap will stay engaged while shift is still held down, no matter how far your mouse moves away from the line. It also will ignore any object snaps that are not on that line while shift is held down. Object snaps that are directly on that same line will still engage.

Also if you push shift when straight snap is not currently engaged at all, it will enable straight snap to the nearest line.


> Often I happen to have to move an object along, for example, the Z axis, or the surface's normal.
> I would like to lock the moving along that direction.

Yeah it should work for this kind of use - the way you'll use it is to move your mouse around as you currently do to activate the particular straight snap that you want like z axis or surface normal or whatever, then hold down shift and that one will stay locked in while you keep shift down.

So that's coming for the next v3 beta.

- Michael