Allow me to join this thread and share my thoughts about your question regarding payroll expenses.
To record payroll expenses while also using the payroll service in QuickBooks Online (QBO) will be a duplicate, which will throw off your bank balance.
You can either proceed with using the payroll service and record job costing by following the steps provided by @Rasa-LilaM above. Or don't run the payroll service and manually record job costings including payroll expenses.
If ever you need to manually record your payroll transactions, take some time and view the link I provided. It's an article with the steps on how you can enter your payroll transactions manually in QBO.
If you need further help, let me know in the comments below. I'll get you back as soon as I can.