I figured I'd come back and update about how I wound up accomplishing this, partly in case anyone wants to do something similar in the future, partially to give some information about ways people can work with their MB data outside of MB, and partially in case I want to do something like this in the future but can't remember how i did it.
Here's the long-winded back-story:
I'm in the process of upgrading some of my library from MP3 to FLAC. The decision to swap in the FLACs that I had sitting on my computer as archival copies was a no brainer for the space saving aspect. Somewhere along the line something very bad happened: I realized I could hear a difference between the FLACs and my Lame -V0 MP3s. Not a huge difference, but a difference. A little more "presence" - a little less distortion in the cymbal crashes - a little more depth of field.
Once that happened, I realized I was going to have to "rerip" (LOL) some of the more "important" albums that I didn't originally save in FLAC to FLAC. At that point, it became a space calculation. I wanted to focus on things I was actually going to wind up listening to the most. My library is set up as a "library" (everything) and a playlist that is my listening library - Tracks from albums in the library that I want to hear. Everything I listen to is derived from that playlist. I wanted to find out which albums in my library had the highest percentage of tracks that wound up in the Listening Library playlist. My "rerip" (LOL) list would be limited to albums with more than 70% of their tracks in the playlist.
Here's how I accomplished it:
In Musicbee:
1. Set up a filter - Playlist is Listening Library and Type is MP3 and Album Track Count > 9 (to weed out singles and EPs)
2. Filter Library and select all tracks
3. Edit->Edit Preferences->Tags(2)...'send to clipboard' tags: '<Album Artist>';'<Album>';'<Album Artist> <Album>';<Album Track Count>
The third field is to give me a unique key in case there are multiple artists with identically named albums. This way I can still sort by artist or album as needed.
4. Right Click->Send To->Clipboard
I use Libre Calc for my spreadsheet needs.
In Libre Calc
1. Edit->Paste
This opens up the text import dialogue.
Separator Option: Semicolon - String Delimiter: '
Now there are 4 columns A-D and one row for each song in the playlist that meets the playlist criteria.
2. Column E is a formula =COUNTIF(C:C,C1) Copy this to all rows.
This counts each row where the <Album Artist> <Album> field equals the one in this row. In other words, how many songs in the list come from this album.
3. Copy this Column E result to a new column and paste as a number, so that if there are any changes in the spreadsheet there is no change to the result. Then delete the original E and this becomes E
4. Column F is a formula =(E1/D1). This gives you the ratio of playlist tracks to album tracks, one row for each song in the playlist.
5. Copy this Column F result to a new column and paste as a number, so that if there are any changes in the spreadsheet there is no change to the result. Then delete the original F and this becomes F.
6. Change the format of F to a percentage.
7. Select all of Column C
8. Data->More Filters->Standard Filters
9. Change the first "Field Name" to "None", click "Options" and check off "No duplications" then click "OK"
This will give you one row per album artist - album.
At this point, I copied and pasted everything to a new spreadsheet as numbers because I didn't need to do any more calculations on the original data and wanted it to remain static no matter what happened.
10. Sort by column F in descending order.
11. Delete anything below 70%
That's it.