Yes, you can modify the state directly inside a slice reducer in Redux Toolkit. This works because Redux Toolkit uses the Immer library internally, which allows writing 'mutating' logic while keeping the state updates immutable under the hood.
Immer wraps the state object in a proxy, capturing all changes made to it.
Instead of mutating the original state, Immer produces a new immutable state based on the changes.
This lets you write simpler and more readable reducer code while preserving immutability.