You can add a popupmenu to a custom window.

For example, make a .txt file named "listchannels.txt", and put this in it:

Join Channel: ls_joinchans
Who Channel: ls_whochans

Then in your script, add these 2 aliases:

alias ls_joinchans {
  var %a = 1, %b
  while $sline($active,%a) { %b = %b $+ , $+ $gettok($v1,1,255) | inc %a }
  join %b
[color:red]  [/color] 
alias ls_whochans {
  var %a = 1, %b
  while $sline($active,%a) { 
    if $me ison $gettok($v1,1,255) { who $v1 }
    inc %a 

Then in your raw code, when creating the window, specify the .txt file like:

if !$window($+(@List-,$network)) { window -kal $+(@List-,$network) listchannels.txt }

This was scripted in a rush, so there could be mistakes, and optimization might be necessary. Btw I'm curious
why you use $chr(255) for your alignment, it looks kinda odd, but I suppose that is a personal preference.