on *:DIALOG:Greetings:*:*: {
  if ($devent == sclick) {
    if ($did == 5) {
      var %x 1
      while (%x <= $lines(GrChannels.txt)) {
        if ($read(GrChannels.txt,%x) = $did(3)) { halt }
        inc %x
      }
      write GrChannels.txt $did(3)
      did -a $dname 4 $did(3)
    }

if you change that and add a simple # $+ you would no longer need to remember to add the # in the edit box on the dialog

on *:DIALOG:Greetings:*:*: {
  if ($devent == sclick) {
    if ($did == 5) {
      var %x 1
      while (%x <= $lines(GrChannels.txt)) {
        if ($read(GrChannels.txt,%x) = $did(3)) { halt }
        inc %x
      }
      write GrChannels.txt # $+ $did(3)
      did -a $dname 4 $did(3)
    }