@User, you need to add (or uncomment if it's there) this line in your xschemrc:

lappend tcl_files ${XSCHEM_SHAREDIR}/ngspice_backannotate.tcl,

this will export a

ngspice::annotate

command... the command searches for a .raw file in the simulation directory with the same name as the schematic you want to annotate. Then you place in teh schematic these symbols:

ngspice_get_expr.sym

(for combining multiple items saved in raw file into an expression, useful for power calculation, SOA, etc) ,

ngspice_probe.sym

(for voltages) ,

ngspice_get_value.sym

(for all things that are saved in raw file like conductances etc).