Hello,
I'm sure this question is very easy; but I've not been able to find documentation about it (neither the forum or the wiki).
I want to use the option "COD fee", located in "Modules-- Order totals". There is possible to define a fee for the COD option. But I want a percentage of the order for that fee, not a fixed value.
I've tried to just put x% or define a tax rate for the COD fee, but it doesn't work.

Any idea? thanks.