I feel you, while the debugging option is handy for development, it is annoying that you can't easily install the extension permanently.

The way I do it now is to package the extension as zip (no webext needed) with a custom manifest, which can be installed by setting xpinstall.signatures.required to false in the about:config page.

On the manifest side, you just need to include this snippet:

  "browser_specific_settings": {
    "gecko": {
      "id": "[email protected]"
    }
  }