Google Apps Editor Add-on: Can't create test deployment

I have developed a Google Slides Add-on as an editor add-on. I am attempting to get the add-on into a few hands (family/friends) for testing.

• ✅ I can execute the project successfully within Google Slides
• ✅ I have created a Google Cloud Platform project and associated the apps script project with it
• ✅ I have added my handful of users as test users within the GCP project.

I am following these instructions to create a test deployment.

• I open the Slides file that contains my add-on script
• I go to the project settings
• I click the blue Deploy button and then click Test deployments
• I choose the drop-down to select a deployment type

The instructions here say that I should select Editor Add-on as the type. However, it is not available. Google Workspace Add-on is available, but when selecting it I see the message To test deployment as Add-on, update the manifest file with Add-on details and I am unable to create a deployment (presumably because the manifest is different for Workspace and Editor add-ons).

My current appsscript.json manifest:

{
  "timeZone": "America/New_York",
  "dependencies": {
    "enabledAdvancedServices": [
      {
        "userSymbol": "Slides",
        "version": "v1",
        "serviceId": "slides"
      }
    ]
  },
  "exceptionLogging": "STACKDRIVER",
  "runtimeVersion": "V8",
  "oauthScopes": [
    "https://www.googleapis.com/auth/userinfo.email",
    "https://www.googleapis.com/auth/script.container.ui",
    "https://www.googleapis.com/auth/presentations"
  ]
}

Question

• What is the correct way to create a Test Deployment for an editor add-on for Google Workspace from Apps Script that lives inside a Google Slides file?

Things I've Tried so far

• ❌ Modifying my manifest to be a workplace-style manifest using instructions like this. Upon attempting to save the manifest, I see validation errors indicating it's the wrong kind of manifest.