When my component files were in the same directory as my component files, the line

%! TeX root = prd_whatever

allowed processing the component file from the component file. (I use TeXShop for this.)

The project structure has been changed: the component files are in a subdirectory of the directory that has the prd file. Now,

%! TeX root = prd_whatever

no longer works. (E.g., it cannot find the environment files called in the prd file.)

Is there a way to restore processing from the component file. My experiments are near to wearing out the “error” message/page.

Alan