Bookmarks are event markers in the allocation history. You can use the Bookmarks dialog to jump back to a bookmarked location any time.
Bookmarks are only used in the Active Objects and Analysis tabs.
Adding bookmarks is very similar to adding watermarks.
You can add new bookmarks directly from allocation items displayed in the Active Objects and Analysis tabs, using the popup menu options.
Bookmarks added this way are initially named using the .exe or DLL and the function name as in the picture below, but you can change this if you want.
Alternatively, you can add a bookmark at the most recent recorded allocation event:
Managers menu
choose Add bookmark at most recent trace
enter a name
click OK
Or use the option on the Watermarks Toolbar:

The most recent trace event may not actually be visible in any of the displays as it could be filtered or hidden for other reasons.
When a session is active, you can show the bookmark manager to see a list of bookmarks, change their names, or jump to a bookmark location:
Managers menu
Bookmark Manager...
shows the Bookmarks dialog
Or use the Watermarks Toolbar option:

Unlike watermarks, bookmarks are shown in the order you add them.

The bookmarks dialog can only be shown when the Active Objects or Analysis tab is open.
The most useful option in this dialog is the Goto:
•Goto
scrolls the open tab to the selected bookmark and selects it (if it exists in the current tab)
Double clicking on the bookmark also jumps to its location.
There's also a few options for renaming and removing bookmarks:
•Edit...
rename the selected bookmark
•Delete
delete the selected bookmark
•Delete All
delete all the bookmarks in the list
You can't change bookmark locations. If you want to do that, delete the bookmarks you don't want and add new ones.