Let me guide you on where is the best place to access your customers' and invoice lists in QuickBooks, @aaastorageofpres.
Being able to view the list of your customers and their transactions on the QBO Mobile app isn't available. The mobile app is a simplified version of QBO, which allows managing your accounting needs on the phone. However, not all features are accessible in this version.
To view the list of your customers and your sales entries, you may access your account using a browser o your phone. Just open the QuickBooks Online link and go to the Sales tab. This contains the data for all your customers:
On the other hand, I'd like to add this reference that contains details about anything that you need to know on how the QBO Mobile app works: What is the QuickBooks Online app?
If you have any other questions or concerns, you can always reach out to the Community. I'd be happy to help. Keep safe!