mojave safe mode

Check this Apple Support page. It should work.

Start up your Mac in safe mode - Apple Support

Technically since you're using a MacBook Air as described, you can use your built-in keyboard and mouse. But, if this is your first time booting to safe mode and you just want to keep it safe, you can use a wired keyboard. If you don't have one, it's fine.

How to use safe mode on your Mac provides an explanation.

To add to the above good advice, I advise you use a wired USB keyboard.

I must have been decaffeinated when I typed that. 😶