How can I set values in the $conf array using the admin interface?
Sure, you can do this at devel/php if Devel module is enabled and you have access to Devel module's Execute PHP code.

The PHP to do what you want is

variable_set('journal_form_ids', array(
    'fivestar_custom_widget' =&gt; 0,
    'guestbook_form_entry_form' =&gt; 0,
    'imagefield_js' =&gt; 0,
    'img_assist_header_form' =&gt; 0,
    'img_assist_properties_form' =&gt; 0,
    'link_widget_js' =&gt; 0,
    // ...
  ));