Setting up provincial and federal fuel tax on sales and purchases

In Quickbooks Enterprise, I am attempting to create items for all the fuel taxes charged in each province, which are a rate per litre (not a %).  To complicate things, there is GST applied to those taxes.

I tried creating each tax as a Sales Tax Item but GST can't be charged on those.

I tried adding this to a Sales Tax Group along with GST so that it would then charge GST on the tax, but that doesn't allow a dollar rate item for the items in the group, only a %rate.

I tried creating each tax as an Item/Other item (not Sales tax item), but that can't be attached to a liability account (only rev/exp) which is obviously what it needs to be in order to report and submit taxes to the govt.

I see I can make it an inventory item, but that overly complicates the books with extra unnecessary accounts etc. and still doesn't allow for a liability, only rev/cost/asset.

I feel I am missing something basic.  Can anyone advise me on how to accomplish setting up fuel taxes per litre in the system properly?

Thanks.