Press the Windows key using "keyboard.press();"
They Keyboard.press() command accept modifiers per the documentation. You may need to do multiple press() commands before releasing.

For example, if you want to launch File Explorer you could use:

Keyboard.press(KEY_LEFT_GUI);
Keyboard.press('e');
Keyboard.releaseAll();


This is equivalent to shortcut keys Win + E.

The modifier GUI is what stands in for the "command key" which is the Windows Logo on a PC or clover (⌘) on a Mac.

I don't have any restriction on the higher value on my board (Pro Micro), as indicated by @frarugi87.