If your question regards only visualising KS-MOs, there are a number of possible solutions, including Molden, GaussView, Chemissian, Molekel and many others. I personally tend to use most often GaussView. Molden is a free option, and very effective: you can have the isosurface contour drawing or a 2D projection.

Thank you. The question is regarding the contour value on FMO diagram.

I have submitted an article to a journal recently, one of the reviewers suggested as "Figures 2-4. The captions should be 'Frontier molecular orbitals for…' The contour values should be given".

Now I see the point. In a Molecular Orbital drawing, the ‘extension’ of the isosurface depends on a threshold value referred to as contour isosurface value or cutoff isosurface value. This generally ranges between 0.01 and 0.05 |e|.

So when a new MO picture is prepared for a publication, the cutoff value adopted must be described in the caption.

Thank you very much