Windows: Shift+Alt+A
Linux: Shift+Ctrl+A
Here you can find all the keyboard shortcuts:
Windows VSCode Shortcuts
Linux VSCode Shortcuts
PS: I prefer Ctrl+Shift+/ for toggling block comments because Ctrl+/ is shortcut for toggling line comments so it’s naturally easier to remember. To do so, just click on the settings icon in the bottom left of the screen and click ‘Keyboard Shortcuts’ and find “toggle block…”. Then click and enter your desired combination.