Assumptions

Initially there are a few customers, defined in data.json

Briefings

Created a DataTable component as a main UI to manage customers. UI's update like edit mode or add a new row are managed by component's state.
The change of data of customers is managed by redux
The reducer comprises of two parts. First, return the next state after an action dispatched. Second, persons object in reducers.ts is considered a database of all customers. When add or delete happens, the persons object gets updated accordingly.

Move the update of persons object in reducer function's third parameter enhancer as a middleware. It will help split the logic between UI related data - states and the data layer - persons object. In real cases, it is more likely the customer data is from a web service.
More tests ....