The tutorial video below explains how different expense transactions are entered in QuickBooks Online. It is a step-by-step process of learning how to enter expenses in QBO. This is probably the best in-depth video that covers vendor expenses in QuickBooks Online. I highly recommend you to watch it.
Let me summarize the content of this video:
It explains how to enter expenses like debit card, credit card, ATM, cash withdrawal, bank fee, wire transfer, write check, enter Vendor Bill to pay later as A/P, Pay Bill by the Check and create Purchase Order and more.
It explains how to set up and enter billable charges to customers.
It explains how to set up and enter expenses by class tracking and location tracking.
Lastly, it explains how these entered expenses will show up on various financial reports.