If you prefer keyboard to navigate between tabs, the Navigator add-in provides NavigateToNextTab and NavigateToPreviousTab commands. Plus core Tabs Studio provides NextTabExtension and PreviousTabExtension commands to switch between windows in a tab group. Using these commands you can switch to any open document using keyboard, but it requires four keyboard shortcuts.
I’ve added two more NavigateToNextWindow and NavigateToPreviousWindow commands to Navigator. These commands first switch to the next document in the selected tab and then switch to the nearest document in the next tab. Now you can switch to any open document using keyboard with only two keyboard shortcuts:
Download link: Navigator v1.0.6.