I have already set a new folder called _build for separating and including the generated aux and bib files of pdflatex and bibtex in Texstudio (with Miktex) as follows:
Texstudio --> Options --> Configure Texstudio --> Commands:
pdflatex.exe -synctex=1 -interaction=nonstopmode --aux-directory=_build %.tex
bibtex.exe _build/% -include-directory=_build
The above configuration works fine and the PDF is output as desired.
However when I tried to do the same with makeindex (using \usepackage{imakeidx} and \makeindex in the preamble, and \printindex in the body document) and then I changed the configuration of makeindex in Texstudio commands as follows:
Texstudio --> Options --> Configure Texstudio --> Commands:
makeindex.exe _build/%.idx -include-directory=_build
Although I see the myfile.idx created in the _build folder but the Index is not created in the document and I receive this message:
Input index file myfile.idx not found. Usage: makeindex [-ilqrcgLT] [-s sty] [-o ind] [-t log] [-p num] [idx0 idx1 ...]
Is there a way to include the new folder path _build correctly in the makeindex command?

_buildfolder and pasting it in the root folder (next to myfile.tex) and then recompile. The index would then print fine. But that's not what I want. I'd rather, if possible, to follow a similar configuration as I did topdflatex.exeandbibtex.exeand apply it tomakeindex.exe. – hesham Jan 26 '19 at 11:16Input index file myfile.idx not found.message. – hesham Jan 26 '19 at 15:32_buildfolder altogether as I see makeindex looks pretty difficult to reassign as you said and "enough potential issues without yet another." – hesham Jan 26 '19 at 17:43