Still, wouldn’t the list of continent-lists be stored as an array in Redux?

Yes, generally something like expanding an accordion component can just sit in the local component state, as long as the collapsed state doesn’t need to affect or be affected by other app state.

I wouldn't store it as array in Redux because that would be too limiting (e.g. let's say I want a continent-list which is decoupled from the other continent-lists). If I would be forced to use redux in this case then I would create some random id for each ComponentList where I would store the UI state (but keep the continents data separated). Something like:

  {
    '<randomId>':
    {
        Asia:
        {
            collapsed: true
        }
    }
  }

IMHO this really makes things unnecessary complicated. It also makes it hard to re-use the ContinentsList component (maybe you want to use the same component in some other project which uses something else than redux?). I always try to think of the API of my react components first and how they later on can be easily reused. After I figured out the API of the react component then I might connect it to some store.

Probably the ContinentsList component would somehow look like this:

  <ContinentsList
    continents={<continents data>}
    renderItem={({ collapse, isCollapsed, continent }) => {
        return <ContinentItem onCollapseClick={collapse} isCollapsed={isCollapsed} continent={continent} />
    }}
  />

I’m still having trouble imagining an application where you would need ContinentLists in different spots without some well-defined arrangement of them in the Redux state where each can be identified by something more concrete than a random ID.

Yeah, I agree that this is an edge case (nothing that I run into on a daily base) and the ContinentLists example might not be the best in this context. Something like a Dashboard with dynamic widgets would probably be a more realistic case.