Persistent Fieldsets

This module makes the state of collapsible fieldsets persistent (If you collapse it, it will remain collapsed). It's a small usability improvement that makes pages like the Modules page a lot better.

You can make any fieldset persistent by adding the #persistent attribute to it.

Example :

$form['block'] = array(
  '#type' => 'fieldset',
  '#title' => t('Block configuration'),
  '#weight' => 3,
  '#collapsible' => TRUE,
  '#collapsed' => FALSE,
  '#persistent' => TRUE,
  '#tree' => TRUE,
);