FlatList: Using an Array vs. Object to Store Data - reactjs

Question

I have a list of objects that are selectable, eg.
let Tasks = [Task A, Task B, Task C, Task D]. I'm using FlatList to render the tasks. Upon clicking a task, user is taken to an "Edit Task" for the selected task. I can use redux to update selected element to the array index or alternatively I can store the selected task key.
case SELECT_TASK:
return {
...state,
selected_habit: action.array_index
};
case SELECT_TASK:
return {
...state,
selected_habit: action.key
};
On the task specific page, the user can edit the task. Then in redux, I could do either of the following:
case EDIT_TASK: {
let tasks = { ...state.tasks};
tasks[state.selected_task] = edited_task; //not showing edit code
return {
...state
tasks: tasks
}
}
//don't use array index, instead use task key
case EDIT_TASK:
return {
...state
tasks: state.tasks.map(task => {
if (task.key === action.key) {
//update task code
return task;
} else return task;
})
}
Within each task, I may have an array of subtasks requiring a flatlist or similar. Accessing these nested arrays using Redux seems messy. It would be seem preferable to hold an object and access specific keys. However, FlatList requires an array.
1) Should I consider storing tasks in redux as an object, and building an array from the object before rendering so I can use FlatList? This would allow be to more easily update specific attributes of tasks (without storing selected states or mapping for each update)?
2) If the current pattern, is there significant performance upside to storing array element instead of object key?