Which mountpoint paths will automatically show up in file browser under devices?

Some examples: - If I plug an external USB drive in, it will get mounted under /media/$USER/ and my file browsers will automatically list the mountpoint under devices. - The same will happen if I manually mount something into a regular folder in my home directory. However, my file browsers will not list the mountpoint if that folder is hidden. - The file browser also won't list mountpoints that are in /tmp, for example. So what are the conditions for a mountpoint to automatically show up in file browsers under devices? Since PCManFM and Nautilus seemingly behave exactly the same, I believe there might be general rules for this? Can I "force" a mountpoint (which is a hidden folder or in /tmp, for example) to show up under devices?