An interesting new accessory for BRIO is the #33981 Large Mountain and Valley Rail Pack. This is not showing up in any of the English-language catalogs for 2019, but it’s available for sale on Amazon in the UK and Germany.
There’s never really been a practical way to get more than two of these Stacking Track Supports at a time from BRIO. This expansion pack gives you four of them plus four of the boulder supports, but it’s an odd way to do it. It also includes six ramps and eight large curves, which don’t really build anything useful on their own. Based on the box photo, which shows configurations that you can’t actually run a train over because there’s not enough clearance, BRIO isn’t sure what to do with it, either. You’re probably better off just buying two packs of the #33253 Stacking Track Supports for less than half the price (total).