A packrat, Jack? Boy, you ain't a-kiddin! Abbotsford gave me the impression that Scott had a serious hoarding problem - rooms full of armor, guns and other weapons, dead animals, a huge and perfect library, and whatnot.

This page (click) from Abbotsford gives the impression that a lot of Scott's papers are there, but perhaps not catalogued yet:

Work is currently ongoing to catalogue Abbotsford’s extensive archive of family letters, diaries, photographs and other written materials. If you would like to enquire about the archive, please contact the Heritage Team.

In the evening after our visit to Abbotsford last month, Steve Byrne and Fiona Hunter of Malinky gave us a concert of songs from Scott's Minstrelsy of the Scottish Border, and it was a delightful evening. Byrne has been collaborating on a Walter Scott Minstrelsy Project. See more at http://walterscott.eu/ - The Resources page is particularly interesting.