@User i have added some (hopefully) useful info in the generated netlist: the full path of schematic (.sch) and symbol (.sym) files are printed (as comments) before any subcircuit, this should help finding out the location of all the source files.

* expanding   symbol:  sky130_tests/bandgap_opamp.sym # of pins=8
* sym_path: /home/schippes/.xschem/xschem_library/xschem_sky130/sky130_tests/bandgap_opamp.sym
* sch_path: /home/schippes/.xschem/xschem_library/xschem_sky130/sky130_tests/bandgap_opamp.sch
.subckt bandgap_opamp  EN_N MINUS PLUS DIFFOUT VCC VSS ADJ START
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.ends