How to make WCFM GST Ready?

As Indian Tax Regulation, we need to collect and submit GST on every sale and margin collected to the Government.
Just want to confirm, how to achieve this GST flow:

For example:

Step 1: If a vendor submits a product of price ?500 to the WCFM then GST will be applied of 5%. After the GST the product will be available at ?500+5% of 500 = ?525 to the customers. (Everything is fine for this step.)

Step 2: If a customer orders the same product then e-commerce operator collects the ?525 from the customer and deduct the margin of 10% from that amount that is ?50. (This step is also fine.)

Step 3: Then again 18% GST will be applied on the margin deducted that means 18% of ?50 = ?9. It means eCommerce operator will deduct ?50 (10% margin on the product price) + ?9 (GST on the 10% margin collected). (I can not achieve this step.)

Step 4: The eCommerce operator also needs to deduct 2% of the product price as a Tax Collection at Source (TCS). It means the eCommerce operator will deduct 2% of ?500 = ?10 from the amount he collected from the customer. (I can not achieve this step also.)

In short: The eCommerce operator needs to deduct 18% on the margin amount and 2% on the product price from the vendor. It means the total amount vendor will get after GST and TCS deduction is as follows: ?525-?50(10% margin)-?9(18% GST on ?50 margin)-?10(2% TCS on product price)= ?456.

But WCFM only deducts the percentage margin from the sale. Please help as the current tax flow is necessary if we want to run the E-commerce marketplace in India.

Thanks.

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