What should I use instead of ui. for fetch data of components of another page?

In AWS App Studio, the ui namespace is limited to accessing components only on the current page, as components are scoped to their respective pages. If you need to access components or data from another page, you should consider alternative approaches:

1. For Amazon Connect views, you can use the "Set JSON" option in the Show view block, which allows you to reference all namespaces in flows, including $.External. This enables you to share data from external systems to your agent in any view you create.

2. In general, for cross-page data sharing, you should consider:

• Using a shared data store or state management
• Passing data through parameters when navigating between pages
• Using automation actions to store and retrieve data that needs to be accessed across different pages

The component scoping limitation is intentional in the design of AWS App Studio to maintain proper separation between pages.
Sources
Using JavaScript to write expressions in App Studio - AWS App Studio
Views: UI templates to customize an agent's workspace in Amazon Connect - Amazon Connect