When loading a new Roblox Studio session, the Quick Open menu (Ctrl + P by default) is not able to be opened. Opening a script resolves this, allowing it to be opened for the rest of the session. This behavior was not like this before. I started experiencing this issue around when the Next Gen Explorer was released.
Expected behavior
Pressing Ctrl + P (or the keybind equivalent for Quick Open) should open the Quick Open menu.