Here’s a really silly little suggestion (well, not that silly!).
When you look at a list of SU/LO files in a file explorer, there is an icon to its left indicating the type of file. At the scale these are normally displayed, the difference between SU and LO files are not obvious. In my case, I often name an LO file the same as its related SU file (makes my life easy), so I then have to rely on the icon or the “Kind/Filetype” column to identify whether it is SU or LO file.
If the LO icon were a different colour (blue say), you would be able to identify the filetype at a glance and without scrolling back and forth in the file explorer dialog box.
Is this what they call a first world problem??