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PhilippeBruno - the
Job Spy plugin has a
Select and Open Arbitrary Programs and Files Tool.
The Job Spy plugin is a collection of tools, Job spying happened to be first cab off the rank.
IIRC Sagethumbs will display ePub cover images (and lots more too) as thumbnails in Window/File Explorer and and so-called Explorer alternatives such as xplorer˛ and Directory Opus
I use Windows Desktop Search (WDS) and X1 Search regularly. Two of my calibre libraries (110K+ and 60K+ documents) are included in their scope, but so to are emails, blog posts, mailing list items etc etc, all told over 850.000 items. I integrate WDS and X1 search results into calibre via the disarmingly simple and incredibly useful
Drop Search Results plugin. In the main I use it to add books to ad-hoc lists created with the
Reading List plugin.
Kovid Goyal has full text search, integrated within calibre, as one of his long term goals. He is currently finalising version 3.0 (enhanced calibre server and web based viewer).
There is also this ==>>
Recoll Full Text Search plugin, I notice someone got its working on Windows last year.
BR