I found out more about &quot;system&quot; addons. There are different <i>types</i> of addons: <i>app-profile</i>, <i>app-system-addons</i>, <i>app-system-defaults</i>, <i>app-global</i>, <i>app-system-local</i>, <i>app-system-share</i>, <i>app-system-user</i>, <i>app-temporary</i>.<p>The &quot;app-system-defaults&quot; (in my case Pocket &amp; Loop&#x2F;Hello) don&#x27;t seem to be shown to the user, but you can find them in the <i>extensions.xpiState</i> config.<p><a href="https:&#x2F;&#x2F;hg.mozilla.org&#x2F;integration&#x2F;fx-team&#x2F;file&#x2F;5f2f4297e6bd&#x2F;toolkit&#x2F;mozapps&#x2F;extensions&#x2F;internal&#x2F;XPIProvider.jsm#l148" rel="nofollow">https:&#x2F;&#x2F;hg.mozilla.org&#x2F;integration&#x2F;fx-team&#x2F;file&#x2F;5f2f4297e6bd...</a>