How to hide(not remove) any contact from Skype list?

Here's a work-around (since no other answers have yet been posted): edit the user in question, putting a "Z" or "z" (depending on sort-order issues) in front of their name. Then that user goes to the bottom of the list. Change the size of the window so those users don't show (unless you have too many other users to fit; but at least the ones you don't want are now segregated to the end of the list).

You can enable contacts category (Skype menu | Contacts | Contacts categories | See all Contacts Category), create new category, let say "hidden" and move contacts you temporary don't want to see there.

In Skype main window, select "Ungrouped" category to see all contacts except those you put in "hidden" category.