Command key when running Mac through virtual box on Windows OS
I would much rather point to this previous question/answer in a comment but my rep does not allow comments.

There are 3 answers: Windows key when running windows through virtual box on a mac

By default it's the right ⌘ (Command) Key.

The left ⌘ (Command) Key does not work because it is set as the Host (Meta) Key in VirtualBox.

And they can be swapped simply by replacing the Host Key with the right ⌘ (Command) Key, in Preferences > Input > Virtual Machine > Host Key Combination.