@Merris-And-Bob0
As @Mike-And-Jane0 said, you need to turn on Pro Tools in order to see & add custom taxes. You can only do this on your laptop/desktop; it's doesn't seem like you can on your phone.
Just to note, Airbnb does not allow custom tax collection in all locations. You'll have to check in the Preferences Section/Taxes and see what they are currently collecting for the listing and if they aren't collecting all the taxes, if you can add a custom tax.