mmmh ok, good one! I don't think it's clear enough:
I would put create two differents paragraphs, 1 for Graphql and 1 for internal libraries use case.

In the internal lib use case, I would take more time to expose the issue:

• in some cases, we want to be able to pass a string amongst a list of string to a library (ex. setHotkeyScopeAndMemorizePreviousScope that can take "relation-picker" | "companies-table" as a valid scope)
• however, the library code should not be aware of this specific list which is only a concern for the library api user. We don't want developers to add a new possibility to the library each time they need it. This means the library will accept any string as a valid input. setHotkeyScopeAndMemorizePreviousScope(scope: string)
• in this case, we use enums to make sure that we are passing an authorized scope to the function (RelationPickerHotkeyScope.RelationPicker | AppHotkeyScope.CompaniesTable)