No problem at all. I would create a new code for it, but include it in Direct Expenses. Overheads are more like Admin costs which are the general costs of running a business, like office expenses, telephone, that type of thing. They are not specific to any particular type of business.
Direct Costs are costs that are directly related to the process of selling your products or services, but which don’t fit into cost of sales. If you stopped selling them or switched to something else, you wouldn’t have to incur those costs, whereas you would still have to pay telephone bills etc.
Cost of sales are simply the costs incurred in bringing your product to market, so generally speaking they relate to goods and are either the cost of buying goods in for resale, or the costs of manufacturing or processing those goods to get them ready for sale.
Feel free to message me directly if you have any other questions.