I appreciate you for adding clarifications to your concern, pierrel.

At this time, the option to add more than one Approved By lines on Purchase Order is unavailable in QBO.

I will consider this as a suggestion on how we can improve our purchase order customization feature. That said, I'll be forwarding this idea directly to our Product Development Team to be part of their future product enhancement deliberation.

In the meantime, I encourage you to check out our QuickBooks Blog for any enhancements and announcements about the QuickBooks Online product. 

You know where to go if you have other QuickBooks questions. I've got your back. Wish you all the best!