Freight Cost + Warranty Charge

My freight company charges me a freight cost and any additional fees payable e.g. if product is lost or damaged then an amount is paid to me is classified as warranty.

For example:
Freight Cost: $36.00
Warranty: $4.00

GST is payable on Total amount of $40.00.

Firstly all my products that I sell to the customer are inclusive of freight i.e. free shipping. This means I dont add it to the sales invoice and create a seperate expense. Firstly is this the correct way to do this?

Secondly, would I have a separate account for warranty in expenses and add the warranty charge in that expense account?

Thirdly, how would I add both the freight and warranty together? Would this be as a journal entry?

You are correct in creating a separate expense if your sales invoices include freight.

A separate account for freight and warranty expenses depends on your own information needs vs the simplicity of combining the expenses.

If you want to merge freight and warranty accounts together, you can rename one of the accounts to the same name as the other account then use the Find and Merge facility in the Chart of Accounts.