Muse muse (10.04) tracked it down for me:

On A Rainy Afternoon/Does She Need Me?/I Can't Leave Her Behind

Written by Bob Dylan (and Robbie Robertson, I assume)
Filmed in an unknown hotel room during the 1966 tour, and saved for posterity on Eat The Document

Lyrics transcribed by Tobias Levander and Arild Langseth ("I Can't Leave Her Behind").

Tabbed by Eyolf Østrem

This is one of the most charming tunes that Dylan has never written - too bad he didn't finish it. It is also a fascinating study in the development of song, and in Dylan's composing technique. I assume that the version called "On a rainy afternoon" or "Does she need me?" comes first - the "twice as slow" version with the duple time rhythm that grows out of this, is what appears in "I can't leave her behind".

Dylan's guitar is tuned in drop C (C-A-d-g-b-e'), capoed on the fifth fret, Robbie's is in standard tuning.

The main transcription uses Robbie's guitar. Bbmaj7 = xx8765

More information here.