It is not very clear when you are on "Content Structure" and "Media Library". There's the green line below the literals, but not enough in my case. I'd probably change "Content Tree" literal to "Content Structure", "Media Library" or "Users" depending on what you will find...

Or, suggestion:

• in Content Structure: keep "Content tree"
• in Media libary: "Media library tree"
• in Users: "User tree"