Good morning! I have two SVGs: `foo.svg` and `bar.svg`. The `bar.svg` is embedded in `foo.svg`. This is `foo.svg` (note: the weird namespacing is from generated code, but should be legal SVG):

<ns0:svg xmlns:ns0="http://www.w3.org/2000/svg" xmlns:ns1="http://www.w3.org/1999/xlink" height="594mm" id="root" version="1.1" width="841mm">
  <ns0:svg version="1.1" x="150mm" y="50mm">
    <ns0:use ns1:href="bar.svg#root" />
  </ns0:svg>
</ns0:svg>

`bar.svg` looks like this:

<?xml version="1.0" encoding="utf-8" ?>
<svg baseProfile="full" height="57.01824367046356mm" id="root" version="1.1" viewBox="0 0 101.36576652526855 57.01824367046356" width="101.36576652526855mm" xmlns="http://www.w3.org/2000/svg" xmlns:ev="http://www.w3.org/2001/xml-events" xmlns:xlink="http://www.w3.org/1999/xlink">
  <defs>
    <style type="text/css">
<![CDATA[.cut { fill: red; stroke: black; stroke-linecap: 'round'; stroke-width: 0.3px; }
.annotation { stroke: blue; stroke-linecap: 'round'; stroke-width: 0.05px; }
]]>    </style>
    <marker id="dimension-marker" markerHeight="20" markerWidth="20" orient="auto" refX="7.5" refY="10">
      <path class="annotation" d="M 7.5 0 L 7.5 20" style="stroke-width:2px;"/>
      <path class="annotation" d="M 0 0 L 15 20" style="stroke-width:3px;"/>
    </marker>
  </defs>
  <polygon class="cut IfcActuator material-Material globalid-1i8vwtyw50X9xUvs1JXWUl" points="40.68288326263428,38.50912094116211 40.68288326263428,18.50912094116211 60.68288326263428,18.50912094116211 60.68288326263428,38.50912094116211"/>
  <line class="annotation dimension" marker-end="url(#dimension-marker)" marker-start="url(#dimension-marker)" x1="67.6005630493164" x2="67.6005630493164" y1="38.50912094116211" y2="28.50912094116211"/>
  <text font-size="0.2mm" x="38.935245513916016" y="28.50912094116211">2000</text>
  <line class="annotation dimension" marker-end="url(#dimension-marker)" marker-start="url(#dimension-marker)" x1="40.682884216308594" x2="60.682884216308594" y1="16.595041275024414" y2="16.595041275024414"/>
</svg>

-----

If I open up `bar.svg` in Inkscape directly, the #dimension-marker displays as expected, in blue. If I open up `foo.svg`, the #dimension-marker does not display in the embedded `bar.svg`. Ideas? The CSS in `bar.svg` still applies, though, so that is a sign that it is reading the <defs> tag in `bar.svg`. Why would the #dimension-marker not show?

Let's continue at https://gitlab.com/inkscape/inbox/issues/1363

@Moult Please try to avoid cross-posting, and if you do make sure to link between the reports.