Or Safari App Extensions vs Safari Extensions
In SafariBrowserWindow you can get an array with all the tabs in the window, and also the active tab: .tabs, .activeTab.
In SFSafariWindow you can get the active tab only: getActiveTab()
Similarily, in SFSafariApplication you can get the active window only, not a collection of open windows.
I need the tabs and windows collections to be able to port my extension. Is it possible?