A simple GUI that replicates the behavior of the default Roblox Studio Explorer. To use, insert into a player's PlayerGui through some means (StarterGui or otherwise). The 'UseDark' BoolValue in the main ScreenGui object toggles between Light and Dark theme and can be done at any point during running.
Also, the pause/play button on the title pauses or resumes updates for the GUI and the SelectedObject ObjectValue lets you tell what a player has selected with this GUI.