Remember Where Left Off in Previous Session

One of these should do the trick.

If you are just closing the Opus window and then re-opening it later on:

[ul][li]Preferences / Launching Opus / Default Lister / Update Default Lister automatically when closing a Lister[/li][/ul]

If you are fully exiting Opus (or restarting the computer while Opus is running):

[ul][li]Preferences / Launching Opus / Startup / Open the Listers that were open when the program was last closed[/li][/ul]