Added in 1.9.0

/alias [filename] <aliasname> <command>

Add/remove/replace any single line alias.

Parameters
[filename] - An optional alias filename to update, if no filename is specified it will use the first match or the first loaded alias file.
<aliasname> - Name of the alias to add/remove/replace.
<command> - The command(s) to be executed by the aliasname.

Example

;This will replace the first matching alias with the new command.
/alias /hello /me says hello

;To remove an existing alias:
/alias /hello

;If you want to add/remove/replace a alias in an existing file
/alias hello.txt /alias /me says hello