What's the shortcut for plus (adding) and minus (removing) by default In list elements inside System Preferences, I see a "plus" and a "minus" to add or remove elements (see photo below for example of Networking System Preferences). 



In Windows these are usually associated with Insert / Delete or AltA / AltD. Is there keyboard shortcuts for these keys? I am trying to add keyboard shortcuts in preference without using a mouse but I have to rely on tab key to achieve this.
Alt 0177 ±
Hold ALT key and type 0177 on keypad

https://fsymbols.com/keyboard/windows/alt-codes/list/