To create a custom app for a new team of service agents, a UX Designer could customize the following parts of the user interface:

Tabs within the app’s navigation bar: This allows the UX Designer to select which tabs are visible and accessible for the app users, such as Accounts, Contacts, Cases, etc. It can help the UX Designer to tailor the app to the specific needs and tasks of the service agents.

Page layouts of the records: This enables the UX Designer to control how the fields and related lists are arranged and displayed on the record detail pages, such as the Case page layout. It can help the UX Designer to optimize the information architecture and usability of the record pages for the service agents.

Details to be shown in the records highlights panels: This allows the UX Designer to choose which fields and actions are shown in the highlights panel at the top of the record pages, such as the Case Number, Status, Priority, etc. It can help the UX Designer to emphasize the most important and relevant information and actions for the service agents.