There are many filters you can use for the addresses.
Clear: Clears the filter.
Category: Sets the filter to the category of the currently selected address.
Dialog: Brings up a dialog for you to set your own filter.
Text search: You can choose words to filter on. Wildcards are permitted. These words can be in Comments, BriefName, DisplayName, or Organization.
SentTo: Only the names in the sent to list.
Not Once. This filter is saved across sessions. If an address has Once checked, it means that you used this only once. Check the Not Once menu, and you will see only addresses with Once not checked.
Record. Only address records >= to the presently selected record are shown. This way you can make modifications to recent records.
Flag. You can set a flag for an address record. Pressing Set Flag will set or clear the flag from the entire (filtered) address table. Press Flag Only to see only records with the flag checked. Press No Flag to see only records with the flag not checked. This is useful if you have a group of addresses that you wish to focus on in some type of mass mailing, and you do not want them confused with other addresses.