Are the fields for ADDITIONAL_FEES listed somewhere?

[tanyaunangst]

I would like to display the fee amount for tax instead of the percentage.  The code in the example line items table is like this (below).  But the Modern quote template displays the tax as a dollar amount instead of the percentage.  I'd like to do the same on our custom template but I don't know what field is used for the tax amount on an additional fee. I haven't been able to find the html for the Modern Template anywhere. 
Does anyone know the field for the fee dollar amount for tax, or are all the fields documented anywhere? 

{{ fee.category == "DISCOUNT" ? "-" : null }}
{% if fee.is_percentage %}
{{ fee.amount }} %
{% else %}
{{ fee.amount|format_currency(LOCALE, CURRENCY, true)}}
{% endif %}