The midnam and middev specs were put together by the MIDI Manufacturers Association, so you might want to check their site; but, the last time I looked, there was no info.
I wrote a middev editor as part of CherryPicker (2.62) and basically used all the tags I'd come across in looking at whatever files I could find put out by MOTU, Digi, and others. My gut tells me that none of the apps that use midnam/middev actually respond to 99% of the values in a middev file - all they really care about is that the file exists, and that its name/manufacturer correspond to the midnam - which contains the name info. They might also respond to the bank select switches.
The basic problem with all the midnam/middev stuff is that each DAW implements a different subset - and none (AFIK) uses all of the available tags. MOTU files are not always compatible with Digi etc. I wrote an app called CherryMangler that converts an entire MOTU folder into a Digi compatible one - it also generates a Digi middev file. If you use this, you can use CherryPicker to add expansion patch names to just about all synths, since MOTU includes them in their distribution - and there are many sites where you can download the MOTU folder.
I'm not trying to plug CherryPicker, since I put it out as basically freeware - but you might find it useful to look at the documentation (which is on-line) where I try to explain some of the nuances of midnams/middevs.
(
www.alterspective.com/cherrypicker)
Cheers, Rob