Razor Appswitcher Setup - Razor-qt/razor-qt GitHub Wiki
Most Window Managers (WM) use own implementation of famous Alt+TAB shortcut to switch opened windows or applications. You will need to setup it manually if it is not available in the WM of your choice, or if you want to use Razor-qt's own solution.
Open razor-config-session
tab Autostart and enable the Razor Autostart/Application Switcher.
Warning: You will need to disable WM native application switcher if it's in use.