Middle-mouse is different than double-click. There is no built-in pref for disabling middle-mouse for closing a Tab.

Is this someway possible? For most users this is OK, but 1 employee using accessibility (mouse)pad and there is very easy make unwanted double click. I not find way how to disable this. I also not found this setting in Windows10 OS.

Perhaps there is an extension that adds a feature like that to Firefox; I am not aware of any like that though.

Look thru this search for "Tab" extensions. https://addons.mozilla.org/en-US/firefox/search/?q=Tab