Hi there, alex44.
We're currently unable to select an employee from the payee section of an expense, or other transactions using the mobile app.
I can forward your suggestion to our product engineers for a feature request. We always update new features in QuickBooks, and this might be included in the future.
In the meantime, please use either a mobile browser or a supported web browser to create expenses in your QuickBooks account. You can check our supported browsers in this article: System requirements for QuickBooks Online.
Feel free to get back to us if you have additional questions related to your concern. Thanks.