Sales Order new function

Can we add a function in the sales order that we can add cost line by line and this function is only for the business owners not for the customer?
In this way when we are in operations related to the sales order we can add cost description and amount
of cost then at the end of the business, we can see cost details with the total amount of the cost. It would be nice if every cost line should have different currency options.
As an example case ;
A business called "Engine Overhaul " has lots of costs during the operations such as Labour, Materials, Rent car, etc… Labour cost I should have an option USD/Euro/TRY currency option and I should choose whatever I want. Also, the exchange rate can be inserted in the cost line where I want it.

Can this function be added to the sales order?

Welcome to the forum. In the future, please limit posts to a single topic, especially when requesting new features.

For this, you should use a sales quote and select the option not to include prices. Sales orders are meant to be internal documents in response to an order from the customer.

That isn’t possible. The currency of a sales document (quote/order/invoice) is determined by the customer, not the line item. If you tried to do that, you would not be able to obtain a total. Exchange rates are entered in the Settings tab. They affect balances of many accounts. That is also not something you can select line by line. You cannot, for example, add dollars converted to euros at one rate to euros converted to dollars at another rate on the same transaction and have it mean anything.