Originally Posted by Lady Fitzgerald
Sadly, different custom and hidden columns is one the two major reasons why I need separate libraries (the other being I do not want my sheet music and books junking each other up).
So you just need to change your config. According to Charles, a simple batch file, with two lines will do it. Exit Calibre, click batch file #2 and it will start with library #2. Exit again, click batch file #1 and it will restart with library #1. Each will have different columns.
Or, if you prefer, you can log out and log in as another user.