Any event of interest can be tagged with a bookmark.
To add a bookmark, double-click the left margin next to an event, or right-click the margin and select Add bookmark. Alternatively, use the menu. Edit the bookmark description as desired and click OK.
The bookmark will be displayed in the left margin, and hovering the mouse over the bookmark button will display the description in a tooltip.
To remove a bookmark, double-click its button, select Remove Bookmark from the left margin context menu, or select Delete from the Bookmarks view.