I desired Safari extension to enable displaying a lot of tabs with multi rows like Tab Mix Plus which is a one of extensions for Firefox. This extension is very useful for me, but there is no extension like it at least I was looking for. And I wondered why no one create an extension like it.
But, I found there is a good way to look for a specific tab from a lot of tabs opened in Safari window at the same time. That is,,, pinch with two fingers on Safari. This action shrinks current tab size and these smaller tabs can be changed by drag with two fingers swipe. I favorite this way and will use this way in the future.