@Stefan Schippers In attached schematic waveform for current through ammeter is not getting plotted in internal waveform viewer. Can you please suggest what might be the issue in this schematic ?

See the corrected schematic. Added (uncommented) a

save all

and changed the "load waves" launcher to load dc instead of tran. :

tclcommand="xschem raw_read $netlist_dir/nmos.raw dc"