insert other taxation (excise) addition to v.a.t.

Hi,

You want to create a new "tax category" via the button "manage tax categories" of the System>Taxes menu.
Then create also a tax rate via the "manage tax rates" button next to it for this tobacco tax.
Then, set that tax category for your tobacco products.
Then create tax rules for this tax category where each tax rule has the "cumulative" option turned on so that both the normal tax rate and the tobacco tax rate can be added to the products of that tax category.