Add surcharges as a percentage

At the moment it is only possible to calculate the surcharge for Sundays, public holidays etc. as a percentage. However, this is a lot of arithmetic as we have employees in different positions or hourly wages. It would be very helpful if the surcharge were generally based on a percentage, e.g. Sunday 80% regardless of the hourly wage of the respective employee. This would then be calculated automatically for the day in question and would also be visible in the wage time or hours export as before.

Many thanks in advance!!!