@User: It appears to have something to do with the fact that I used an absolute path for

XSCHEM_START_WINDOW

. According to the comments in

xschemrc

, I should be leaving

XSCHEM_START_WINDOW

as-is, because it says it should be a path "relative to one of the XSCHEM_LIBRARY_PATH directories.". But this does not seem to be the case. I have the right directory added to

XSCHEM_LIBRARY_PATH

, so according to that statement, if I left

XSCHEM_START_WINDOW

as

sky130_tests/top.sch

, it should have worked. But it doesn't; I instead get the error

Unable to open file: /home/tim/projects/xschem_test/xschem/sky130_tests/top.sch

. So it is looking in my current working directory, which I did not add to the library path, and not looking in the directory which I did add to it.