Sweet Home 3D doesn't allow to hide levels under an other one. Display selected level real name should be Display selected level and levels below. The only workaround would be to edit this level in a separate document.

I am on the french version and switching language to english, does not seem to update the "levels" names as they remain called "niveaux"

As you are free to name a level as you wish by double-clinking on its level tab, I chose not to rename levels automatically when you change the language in the preferences.