1. Edit a file in PL
2. Save to the desktop as a jpg
3. Close PL
4. Look for the file thumbnail on the desktop. It's not there.
5. Right click on the desktop and select "Refresh"
6. The thumbnail of the mysterious file appears.
I have tested this with PL 32 and PL 64. The behavior is the same. Files in gif, png, and tif all produce thumbnails after the refresh. A PLD file appears as a generic PL icon after refresh. How a PSD file behaves after being saved to the desktop by PL seems to depend on what direction the wind is blowing or what I had for lunch today. Sometimes it will be a thumbnail and sometimes it will be the generic icon for my default viewer after Refresh. (I do have the PSD thumbnail utility installed.)
Anyway, all of this seems odd. All the other applications I have will produce either a generic icon or a thumbnail on the desktop if I save a file there -- without having to do a desktop Refresh.
Bob