According to your questions:
Q1 - "Attachments must be added through Shop Manager one by one. Very slow when there many to do."
Attachment is unique file, that's why to upload it - we need to organize 1 FTP connection to server.
When you added 3 or 10 attachments in bulk, all files will be added in FTP queue for upload.
Q2 - "A csv import for Attachments would allow upload much faster. Or allow FTP upload of any number of attachment files."
All the same with import. See me answer for Q1
We can speed up Upload process by increasing of FTP threads - see Preference Window - FTP section - Additional - Max FTP threads
pic - http://screencast.com/t/E3NCOSfZ2S
Q3 - "The Attachment screen ONLY shows Attachment ID, Name, File Name and Original File Name. It does not permit showing Product Reference, or anything about Products that an attachment is used for."
According to PrestaShop Backend we have:
ID, Name, File hash
pic - http://screencast.com/t/kR4zru0sPuLv
All the same and more we have in Store Manager:
ID, Name, Filename hash , original finemae (new field)
pic - http://screencast.com/t/hrIkjzg0Kr
According to your suggestion: you want to add Reference between Attachment and selected products were assigned.
Am I right ?