It's lovely to see you here today, R-keim,
I can add a bit more about choosing the expense account for your reimbursements item.
QBsguru's answer is correct. You can add a reimbursement/addition item before you can add it to a specific expense account. You may refer to this article to set up a reimbursement pay type:
Once done, you can now set the reimbursement's wage expense account in the Preferences section of the Payroll Settings. Let me guide you how to do that:
That should point you in the right direction, R-keim.
Please feel free to fill me in if you have any more questions with QuickBooks Online Payroll. I'll keep an eye on this post for your response. Have a great day!