To elaborate a bit, I just opened a file that for some reason has only about 25 chord suffixes in the chord suffix selection dialog box, when I normally have about 175. It seems to me those suffixes would be best stored with the program files, not individual documents, since you certainly don't want to be forced to do them over from scratch.

This is why it makes sense to use a custom template. In it you have all of the chord suffixes you use, and you begin all projects from that file.

To answer your first question, in your document with 175 suffixes, choose save library, chord suffixes. In you other document, choose load library and choose the library you just saved from the other file.