Tinkergnome,
The purpose of the Post Processing option "Display filename and layer on LCD" is to do exactly that. On the LCD screen where the filename of the object being printed is shown, this setting should then display the filename and the layer currently being printed.
My understanding is that you could put any text you want in the "text to display" field i.e. Merry Christmas, Happy Printing, Be Happy! and that would appear on the LCD instead of your filename currently being printed.
In the Post Processing there are also several other options such as "Pause at height", "Filament change", etc.
What I am trying to achieve is to learn why the post processing options do not work for me.