Using UUID or GUID in the Generator

You can use external...executeBlocking to call a command that sends its results to a text file, and then read that into a variable.

Absolutely! MERL has associative variables, so they can be used as a map.

While writing out your Channel list, you grab the uuid and store it in a variable named after the Channel. If you have channels called A and B, the code below will store their UUIDs in $channelUuidA and $channelUuidB.

foreach .Channel
{  _nextUuid() /* sets $uuid, define as in 2nd block above */
   'this.addChannel(' id ');' newline /* or however you write your list */
   variable
      'channelUuid' id /* the name of the variable, cf. key of map */
   write
      $uuid /* the value of the variable, cf. value of map */
   close
}

You can then later grab the UUIDs when you need them in a similar way, with variable...read. E.g. iterating over the Cartesian product of Components and Channels and writing out a connection for each:

foreach .Component
{  do .Channel
   {  'this.addConnection(' id;1 ', '
      variable 'channelUuid' id read
      ');' newline
   }
}

id;1 is the id of the object one level further out in the loop nesting (or further back on the stack), i.e. the Component here.

You might want to build your variable names based on the oid rather than id, if the channel names aren't sufficiently unique. And of course if you prefer arrays, that's possible too: just build the variable names with numbers instead (there are earlier posts on arrays in generators and using arrays in sub-generators). There is no particular format or syntax to the variable names, and no restriction on what characters can be used when building names like this with variable/local...write/read.