svg : what does "use xlink:href" mean in Inkscape?

Question

Is the blue circle a "node" - or what - in this screenshot, and what can be done with it?

Are the only edits (via GUI) going to be by clicking the individual circle? Will "stroke" make a point (I don't think it does). I tried hammering on it with obvious tools, and at best could make it into a path with a bunch of nodes and then stretch them all around - but not as a single point, or node, as I would like.

I produced this file using matplotlib in python 3.10. there are Stack Exchange questions-answers I used to get this (provided on request). An example corresponding line in the .svg file is :

    <g clip-path="url(#pd5fa06bc5b)">
     <use xlink:href="#mae68a82f8c" x="236.16" y="93.364364" 
[ skipping the rest ]
style="fill: #1f77b4; stroke: #1f77b4"/>
    </g>

(UPDATE): I just learned the above code can appear formatted like this too:

          <use
             xlink:href="#m90c91bf53e"
             x="163.13676"
             y="247.0155"
             style="fill:#1f77b4;stroke:#1f77b4"
             id="use90"
             width="100%"
             height="100%" />

I want to - and can - use the x,y coordinates to e.g. draw circles. It'd be useful to know what or how Inkscape is treating this in the first place. I am trying to write better Stack Exchange questions so I'll stop here even though I could go on at length.

Answer 1

Use-elements are a way of placing multiple copies of an object without having to duplicate the definition or a whole node-tree. Elements can be referenced by id with the xlink:href attribute.

Inside Inkscape these are usually called 'clones'. You can make a clone of an object by using 'Edit → Clone → Create Clone' or Alt-D (instead of Ctrl-D for duplicates). This has the advantage that you only need to modify the original and all clones update automatically.

To unlink a clone and make it a real duplicate object, you can use 'Edit → Clone → Unlink Clone' or Shift-Alt-D.