I use Inkscape to makes designs for a laser cutter. This seems like a basic questions, but I can't find an answer. How can I draw lines of zero width for vector cutting but also leave them visible? I find that I am frequently changing line widths in order to make them visible but consequently this makes small changes in the widths of the objects. Isn't there a way to draw lines that have no width for vector cuts but are still visible for design work. Please help! Thanks.

Not as far as I'm aware, it wouldn't be a stroke unless it has some width. 0.100 is the smallest that I get (I could be wrong). Would this work - select edit> select all in all layers, then group everything. Then all you have to do is go to the fill n stroke box and select the lowest stroke (0.100) which will set everything to that stroke width evenly, that should give you a uniform cut. If seeing the actual stroke is a problem, so you could go a step further and turn the opacity (from the fill n stroke box), to 0 or whatever choosing works for you. You wouldn't see anything at an opacity of 0. I haven't cut anything in a long time, but personally think it's the issue of having different stroke widths that cause cutting issues, not the actual viewing of the stroke.
let us know if this resolves your issue as I'm not a cutter expert by any means.
dee

You can use View -> Display Mode -> Outline.

For laser cutting you typically (at least I do) export it to DXF and send it to the laser cutter.
So, the stroke width in Inkscape doesn't really matter. Strange things can happen if you have a stroke width of 0, so I wouldn't to this.
In general, I also would recommend to set
Menubar | Edit | Preferences | Tools | Bounding box to use | Geometric bounding box
Such that the displayed object size, i.e. bounding box size is independent of your stroke width. This makes it easier when scaling the object.
When exporting to DXF, make sure that the scale is properly read by the laser cutter's software. It could be that you need to adjust a factor.

I haven't heard of any cutter which requires a zero stroke width. I've heard of some that require extremely narrow width, but not zero. Just out of curiousity, what kind of laser cutter is it?