This is a minor issue—to which I expect the answer will be simple,
something I should know by now but do not. I am just trying to see if I can
streamline a working directory.

In Directory01, I have a number of prd_NameXX.tex files as well as a
Directory02 which contains .tex files  that are to be called on by each one
of the prd_Name.tex files.

Is there a way to identify the TEX root for each of the common files (in
Directory02) so that
the file will be processed when I process any one of the prd files in
Directory01?

I have tried
% !TEX root=../prd_\mystring.tex

with, e.g., \def\mystring{Name01} in the prd_Name01.tex file, but that does
not seem to work—the various .tex files re not found.

What puzzles me is that the environment files in Directory02 are found.
(That they are identified in a prj file in Directory01 does not seem to be
the reason why.)

There is no problem if I move the contents of Directory02 into Directory01.

Alan