These files can be manually edited, but only when the server is offline, otherwise the edits will be lost when the next autosave happens.
FriendList.txt -- Stores the information that appears in the client friend list. This is a cache file and entries are only added or updated when a player logs out.
FriendNetwork.txt -- Stores information on friend lists for each player character. Each player may have a list of friends.
RegistrationKeys.txt -- The list of available registration keys for account creation.
UsedNames.txt -- A database of all character names that have been registered. This database also doubles for internal character lookups by name or ID.
ZoneIndex.txt -- A database of all ZoneDefs present in the game. This master list is used for linking groves to accounts, looking up used grove names, and warp names as well. If a new grove is added, it needs to have an entry here.