The sub-item taxes gives you an overview of your current stored tax rates, these can accessed through Settings > shop > tax.
In this oveview you can manage existing tax rates and create new tax rates (1).
The context menu (2) on the right hand of the table gives you the option to edit or deleting existing tax rates.
If you click on the button to create a new tax rate, a new window will open, showing you the configuration you can make for your new tax rate.
Here you can name it individually (1) and assign it a percentage value (2).
The editing screen for existing taxes is structured similarly to the new creation screen.
Here you can change previously made configurations.
be careful, these are existing tax rates and could have effects on your live operation.
Since you are accessing an existing tax rate, which may be used or still is use on your live system., the calculations of invoices, etc. that have this tax rate assigned may show different calculation.