...
plugin {
  # The path to the user's main active script. If ManageSieve is used, this the
  # location of the symbolic link controlled by ManageSieve.
  sieve = ~/dovecot.sieve
  
  ...

  sieve_dir = ~/sieve

  ...
  
  # Path to a script file or a directory containing script files that need to be
  # executed before the user's script. If the path points to a directory, all
  # the Sieve scripts contained therein (with the proper .sieve extension) are
  # executed. The order of execution within a directory is determined by the
  # file names, using a normal 8bit per-character comparison. Multiple script
  # file or directory paths can be specified by appending an increasing number.
  sieve_before = /srv/vmail/global_sieve/
  #sieve_before2 =
  #sieve_before3 = (etc...)

  # Identical to sieve_before, only the specified scripts are executed after the
  # user's script (only when keep is still in effect!). Multiple script file or
  # directory paths can be specified by appending an increasing number.
  #sieve_after =
  #sieve_after2 = 
  #sieve_after2 = (etc...)

  ...
  
}