I can't imagine this hasn't been requested before - or maybe it's been implemented and I don't know how to do it.
It would be great to be able to collapse the Table of Contents to the first level - or maybe even select a level to collapse to.
Or even if only in the Bibles. After a while, with so many Bible books accessed - they get expanded to chapters which can be cumbersome to scroll through - or collapse them all individually to get a "clean" ToC again to work from.