What problem does this address?

The Block List's current behaviour is to highlight the item in the list that corresponding with the selected block in the editor.

When using the Block List to navigate around very long posts however, especially those that have plenty of nested blocks, the highlighted Block List item might be hidden deep within the scroll overflow.

What is your proposed solution?

Initially raised by @gwwar in https://github.com/WordPress/gutenberg/pull/35817/files#r736696988, it might be worth exploring whether we could jump to the Block List item when a block is selected, even if that item isn't in the viewport or hasn't yet loaded in the DOM.

It would interact well with efforts to expand nested list items.