wifi icon is removed by mistake

There should be a 'click-box' in Network preferences within System Preferences

that when clicked, should return the visual tool to the Menu bar in your macOS.

The option box usually says to some effect: "..Show wi-fi status in Menu bar.."

Not sure if a restart in Safe mode could help, if menu default is unchanged.

System Preferences-->>Network and that will open up the window shown above. Make sure that Show Wi-Fi status in menu bar is selected.

Axel F.