Hello Maren,
thank you for the quick response. This already helps a lot!
if you'd like to use a 'safe' extension that has been released under the GPL, try https://gitlab.com/su-v/inx-debug/tree/master/src (selected_nodes.py + .inx)
Thanks for this hint. This works fine with Inkscape 0.92 for me (though not with 1.0, see below), and I think I will be able to simplify it according to my needs.
In Inkscape 1.0, the coordinates displayed in the program will better match those printed out by the script (the Y axis will be inversed). Will that be enough for your purpose, or do you need the y axis in a specific direction?
This is very good news. I need to have the correct values for the x axis only, the Y axis doesn't matter, so this would already solve the problem. I just compiled Inkscape 1.0 beta1 (under Linux), but both extensions (exportxy.py and selected_nodes.py) stopped working (they still appear in the "Extensions" menu, but are greyed out). Did I miss something?
Best wishes, Jens