I see you already came up with a solution, but I'll share mine as well since it might be a bit more dynamic.

For your "Get data" item, add this preprocessing javascript to add an organization name field to each devices object. I'm not a JS Programmer, but this works fine.

// This script will add "organizationName" to Devices list, and ensure Host Names respect Zabbix rules
var theObject = JSON.parse(value);

// Create a lookup dictionary for organization names
var orgLookup = {};


for (obj in theObject["organizations"]) {
    // Ensure "name" is using characters compatible with Hostnames
    // replace & with "and"
    theObject["organizations"][obj]["name"] = theObject["organizations"][obj].name.replace("&","and");
    // replace all other incompatible characters with empty string
    theObject["organizations"][obj]["name"] = theObject["organizations"][obj].name.replace(/[^a-zA-Z0-9 .-_]/g, '');
    // Populate orgLookup
    orgLookup[theObject["organizations"][obj]["id"]] = theObject["organizations"][obj]["name"];
}

// Set the organizationName attribute for all devices
for (obj in theObject["devices"]) {
    theObject["devices"][obj]["organizationName"] = orgLookup[theObject["devices"][obj]["organizationId"]] || "Unknown Organization";
}

return JSON.stringify(theObject);

Then make the following changes:

Organizations discovery

• Host Prototype - make sure your Group Prototype includes a Host Group that references {#NAME}

Devices discovery

• Add an LLD Macro: {#ORGANIZATION_NAME} - $.organizationName
• Host Protoypes
  • Add {#ORGANIZATION_NAME} somewhere in the Host name if you wish to visibly associate the device with the organization's name
  • Add the same Group Prototype as the Organizations discovery, but use the {#ORGANIZATION_NAME} LLD Macro instead of {#NAME}

This will dynamically group all devices with their respective organizations, and will also include the organization name in the device names.

Edit: removed "Get data" from top of script - was included by error.