FWIW, here is my Save to Disk template:
Code:
program:
switch(current_library_name(),
'Library - Main',
template('{#path:re(\.,/)}/{series_index:0>3s||_}{#subseries}{#subseries_index:0>3s||_}{title}'),
'Library - Special',
template('{#path:re(\.,/)}/{series_index:0>3s||_}{title}'),
'Library - In Progress',
template('{author_sort}/{series}/{series_index:0>3s}_{title}'),
template('{#path:re(\.,/)}/{#seriesid:re(\.,/)}{#titleid:re(\.,/)}'))
Note that "path" is a custom field I set up, not the path to the file. (In hindsight I should have named it something else)