Hi Huib, thanks for posting on the Community.
Currently, there is no function for components & services in QuickBooks Online. Instead, products & services can be selected on the item details table when entering expense transactions (bills & expenses) for the purposes of re-ordering stock. Then, QuickBooks will increase the quantity on hand in your product & services by the number of items you received. If you're not re-ordering stock, you can instead select the relevant category (chart of account) on the category details table when entering the bill/expense.
If you'd like to submit feedback for further features in QBO, please click the Cog > Feedback in your account - this way, your suggestions will be sent to our product development team who regularly review & implement changes.