I checked your proposal, now I do following:
1. Run schPlot() and plot to file
2. Run ls -al >> ls_log in the folder with generated ps files.
3 Do some postprocesing of ls_log to create the file for feeding the function addnotes.il above.
( I make these actions to define schematics tree and create required file. )
4. After that I open the all the listed in file cells in "s" mode place the note and close the certain cell
5. Run schPlot() again with already placed layout dimensions notes.
6. Create the final PDF file.
But now I do not know how to discard changes in the cells made in point 4. Can you say how to that?