Not sure what would be so difficult about that. Have a panel on the right with the content of what is currently a tab. Then add a suitably styled panel on the left with a list view or something similar. Switch out the right panel as the user changes the selection in the left panel.Unfortunately, there is no way to place tabs on the side of the tab widget while maintaining horizontal text in Qt. If there is, it'll take extensive work to pull it off, I think.
Also, not so sure about the done button. I guess people will call me a bloody minimalist again, but we already have multiple ways of closing this window (3 on most desktop, I think). Do we really need an additional button?