Hi Srilatha,
It's not clear of the requirement, for New tax code creation if relevant conditions doesn't exists in your tax procedure then you need to create new condition for the same and create a Account key for G/L account determination and assigned to Tax procedure.
In above example, you mentioned that it should in the same line item means Tax rate will be 6% + 3.5% or you expecting the tax line item should be same G/L account.
Usually, it will be different conditions for different calculation and generate the tax line item Deductible or Non-deductible based on you configuration.
Can you share us accounting entry how you want it, so it will help us to provide the correct solution.
Regards
Madhava venkat