The jimu-for-builder package is designed to support developing the widget setting page. The setting page is the section of the builder that the experience author adds widget configuration.
Included in the package is the All type, which is a union of the Widget interface and Widget type.
A common use case for this package is importing the All type and then making use of the Widget on callback function. When a setting is changed via the experience author's workflow, this function is called to save the changed value into the widget configuration (e.g. props.id and props.use). This pattern is usually paired with parts of the jimu-ui package. In this example, we commonly use the Map. The function is called when a Map widget item is selected and the use array of Map widget IDs is updated with what the on function returns.
In summary, you will use the jimu-for-builder package when constructing a widget's setting page.