Firefox extension will not load local settings due to an error

I published a Firefox extension recently and wanted to add an options page. However I need to add an extension ID to my manifest file, and adding an ID causes my extension to not work. My last version seemed to work fine without errors or warnings, but now it produces this error:
1590890699733 addons.webextension.{73a94ba2-5eca-4144-8769-6ee6529b3579} WARN Loading extension ‘{73a94ba2-5eca-4144-8769-6ee6529b3579}’: Reading manifest: Warning processing website: An unexpected property was found in the WebExtension manifest.
‘{73a94ba2-5eca-4144-8769-6ee6529b3579}’ is just the temporary extension ID that I copied from the about:debugging page. How do I add an ID in order to get my settings to work?

How are you setting extension ID?
It should be done like this:

"browser_specific_settings": {
    "gecko": {
      "id": "addon@example.com",
      "strict_min_version": "68.0"
    }
  },

See the docs:

If you load your extension with about:debugging you should not need to specify an extension ID to test the options page. Unless you’re trying to test a feature that relies on one of these specific APIs: https://extensionworkshop.com/documentation/develop/extensions-and-the-add-on-id/

Especially using the ID from about:debugging and making it permanent seems like a backward approach to the issue.

If it is published on the Mozilla Add-ons site, then it already has an ID and if you were to upload an update with a different ID you could end up creating a second listing.

If you can’t find your extension’s ID easily, it is in the HTML source of the listing page on AMO. Ctrl+u (or on Mac, Command+u) then use Find in page for "guid" (with the quotation marks) to drill down in the JSON section.

Also, I’m not sure you need an ID in the manifest.json to have an Options page. ??