Tab list, names and chat

effectset tab header of <who> to <text>since 1.5.2

anywhere · Text above the player list. \n makes more lines

set tab header of player to "&6&lMy Server"

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effectset tab footer of <who> to <text>since 1.5.2

anywhere · Text below it

set tab footer of player to "&7Online: %server.online_players%"

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effectset display name of <who> to <text>since 1.5.2

anywhere · The name used in chat and in the tab list

set display name of player to "&6[VIP] %player.name%"

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effectset join message to <text>since 1.5.2

on player join · Replaces "Steve joined the game"

set join message to "&a+ &f%player.name%"

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effectset quit message to <text>since 1.5.2

on player quit · Replaces "Steve left the game"

on player quit:
    set quit message to "&c- &f%player.name%"

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effecthide join message / hide quit messagesince 1.5.2

those events · Shows nothing

on player join:
    hide join message

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effectset chat format to <text>since 1.5.2

on player chat · The whole chat line, built from placeholders

set chat format to "&7%player.name% &8>> &f%event.message%"

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effectset chat message to <text>since 1.5.2

on player chat · Replaces what the player said

on player chat:
    if message contains "badword":
        set chat message to "(removed)"

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Guide and examples

on player join:
    set join message to "&a+ &f%player.name%"
    set tab header of player to "&6&lMy Server"
    set tab footer of player to "&7Online: %server.online_players%"
    if player has permission "rank.vip":
        set display name of player to "&6[VIP] %player.name%"

on player quit:
    hide quit message

on player chat:
    set chat format to "&7%player.name% &8>> &f%event.message%"

Statement	Where	Effect
`set tab header of <who> to <text>`	anywhere	Text above the player list. `\n` makes more lines
`set tab footer of <who> to <text>`	anywhere	Text below it
`set display name of <who> to <text>`	anywhere	The name used in chat and in the tab list
`set join message to <text>`	`on player join`	Replaces "Steve joined the game"
`set quit message to <text>`	`on player quit`	Replaces "Steve left the game"
`hide join message` / `hide quit message`	those events	Shows nothing
`set chat format to <text>`	`on player chat`	The whole chat line, built from placeholders
`set chat message to <text>`	`on player chat`	Replaces what the player said

To keep a header or footer up to date, set it from a timer: every 5 seconds for all players:.
A display name lasts until the player logs out; set it again in on player join.
The name above a player's head cannot be changed this way. Minecraft ties it to the account name; only the chat and tab list names change.
set chat format writes the line exactly as given, so include %event.message% where the message should go. Other chat plugins that set a format of their own may override it.
The event statements only work in their own event and before any wait; elsewhere they log a warning.