customize formula instead of using the predefined formula

Morisa Expensify Customer Posts: 1

How can I customize my tax VAT rate?

for example VAT rate - {expense:tax:percentage} would output 20% assuming this is the amount of tax that was applied to the subtotal; but if you live in different country the VAT (HST) in this case maybe 13% instead of 20%.... How can I customise the formula instead of using the formulas found on this page