Delete All
Delete All is a new step in Online Help where outmoded Chapters are deleted entirely.
Many entries in Online Help are only to document changes which may cause surprise. Now that the new way is the way entries for the old way need to get out of the way.
Chapter 406 was an ragtag collection of changes from various versions and the first to go. It had goodies like larger objects, new comments, and renamed and removed objects past.
Filter List
Filter List lets you narrow the results on a list such as Ship-To Contacts to find fewer.
Clear Filters
Clear Filters resets the Filter entries above columns you are search for matches ("123")