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thank you, that fixed the problem!

Looks like it was an Edge Browser issue.  Just updated from v88.0.705.68 to 88.0.705.74 and the DOC/DOCX files now display properly.  Cheers !!

I should also mention I am using the latest Edge Browser (v88.0.705.68)

Yes, thumbnails are created and display fine for newly uploaded documents.

Older DOC files will also no longer display with the LibreOffice viewer.  The display fine using Google doc viewer or MSOffice viewer.  The LibreOffice Viewer source in the "customizables" folder is encoded so I can't look at that for any help.

Or have a back button after you click on a thumbnail in Grid View?

>> "So, if we are allowed to specify a path for files&folders created by filerun (such as thumbnail&trash)"

You mean this option in "\customizables\config.php" ??

$config['path']['trash'] = 'D:/FileRunTemp/trash';

$config['path']['thumbnail_cache'] = 'D:/FileRunTemp/thumbnail';