Separate scrollable collections list from (collection) vault contents

When you have a list of collections over 30-40 (we have nearly 100 to manage separate customers), when scrolling down the collection list you are unable to see the vault contents without needing too scroll back up. If the Collections list was separately scrollable from the vault contents, or perhaps something similar to how you can freeze cells in Excel.

Following on from a request from 2018

@Dara Improve the collection view