Support for multiple notebook files

It should auto-load (optionally?) last used notebook file. You can check azzCardfile program as an example of multi-file handling logic.

Also, it should somehow be compatible with upcoming tabs, which, as you said, would be sections of ONE notebook file. There are several ways how "multi-db-support" and "tabs/sections of db" features could make friends.

The question here if we do allow working with many db's simultaneously.

If the answer is no, things are simple: the program loads one db file and opens all of it's tabs with their names. When the user wants to switch the db, he picks "File > Recent notebooks > (name here)", program closes current tabs, loads another db and opens it's tabs.

If yes, multiple tabs from multiple files should be handled in some way. Variants:
1. Open all tabs from all files in one row.
    1.1. Tab title has only the name of the tab. However, it's containing notebook file may be shown as a hover tooltip for the tab button.
    1.2. Tab titles somehow name the file containing the tab. Like "<FILE>/<TAB_NAME>" or "<FILE>.<TAB_NAME>".
2. Make two rows of tabs, first for files, second for tabs. Not the best though.
3. Make a droplist for selecting one of currently connected db's. If you used foobar2000, it's customizable UI allows both approaches: selecting playlist by clicking tabs, or by picking droplist items.

Just providing ideas. Anyway, the behavior must be well defined before any implementation.

Thanks for the ideas! Option 3 makes most sense to me, this is how I envisioned it actually.