Is object cloning (Alt+D) between files possible in Inkscape/SVG?
Cloning uses the SVG
<use> element, which in principle could refer to an external file.
I tried modifying another
<use> element to link to an external SVG file to no avail. I'll try harder.
If you need the same part of an SVG updating in several places, you can always import using the Link option, but this is not as versatile as clones.