Status: Solved.
Refer to the 2nd floor for the solution.
"File Filter" in workflow does NOT work for ".tex" file.
For example,
(the search scope has been set)
I found out that all file extensions (.py, .c, .txt, .cpp, etc.) work properly EXCEPT ".tex".
It could be a bug, please fix it. Many thanks!
FYI,
OS: OS X Yosemite 10.10.5
Alfred 3: v3.0 [652]
Note that it's different from the case http://www.alfredforum.com/topic/8569-search-for-tex-file/, which fails
to figure out the correct file extension "public.tex".
FYI, searching all files work well, showing the .tex files, e.g. shown as below