The auto-display (into the relevant section) firstly looks for prefixes then if its not successful it looks at the filename to see if it has any magic words:-
"OPERATOR", "OPERATORS", "USER", "OPERATING" = Operators manual
"SERVICE", "MAINTENANCE", "REPAIR", "TECHNICAL" = Service Manual
"INFO" = Information
"SPARES", "PARTS" = Parts
"RESULTS", "TEST SHEET" = Results
"OTHER" = Other
"ID" = Special code for model number which will open up opportunities to work across multiple database systems without having to rename all your folder structures

also possible a reverse renaming system to look for problems (all future stuff)
If its not successful then it starts looking at the contents of the filenames to see if it can categorise by filename instead.
contains "OPERATOR","USER" = Operator manuals
Contains "SERVICE","MAINTENANCE","REPAIR" = Service manuals
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Search facilities, not thought about searching hard drives but that's a good point! (might be difficult to do non matching really fuzzy searching though) but its worth a go.
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I've been rehashing the file names to the above, so it might be slightly better than the version you have.
Ps, thanks Geoff it's been informative feedback!