I'm trying to draw some shapes that share common boundaries, but may be colored independently or otherwise need to be separate objects.

If I start with an object that has nothing but straight-line segments, then the process is pretty easy, and inkscape helps out by snapping to each node in the adjoining object as you draw it...

Click click click click... bing bam boom. We've got two shapes sharing a border. This is perfect...

The trouble I'm having is when that border contains curved segments (Nodes joined with things other than cusps)...

How can I have the new path I am drawing follow those smoothies and cusp nodes and basically copy their parameters? I feel like there has to be a command or hot key or something I'm missing that would accomplish this. Is there a draw-path by tracing existing path function? I saw something in the documentation about holding Ctrl key for the Caligraphy tool, and then it is sort of aware of the other path. Not really what I'm trying to do, but it got me wondering if the capability exists.

One approach I figured out which works, but it still a LOT of clicks, and requires combining multiple paths is to node-edit the original shape, just click each node along the path I want to trace, copy them, click out, paste (break the node-ends sometimes when it makes a closed shape), reposition, and then complete the feature. Then, I have to go back, click all the segments one by one and combine them all into one shape. This gets me where I need to go, but it's really a time consuming and tedious way to go.

In my weird approach to doing this, I have to "fix" some of the points where the separate objects were combined using the 2 nodes to 1 tool. And then everything is fine.

Hi. If I understood the question correctly, I would create a new shape (rectangle), duplicate the shape to reuse and use the option path/difference.

Thanks Marcos. I don't think I understand what you mean.

Can you be more specific? When I duplicate the shape to reuse, what am I difference'ing ?

I believe that the video attached to the commentary is well understood. When you duplicate the original shape and do the path/difference operation with the rectangle you create, the result will be an object that will fit perfectly with the original one.

http://tavmjong.free.fr/INKSCAPE/MANUAL/html/Paths-Combining.html