At the bottom of https://<jenkins_url>/pluginManager/  there is a "Select: All, Compatible, None". Since the list of plug-ins can be huge it's nice to be able to press "All" and then deselect the few you are not interested in or "None" and then select the few you are interested in.

The same principle applies to Extended Choice Parameter when you have a big list of checkboxes, but no "All" and "None" buttons are available here. Adding them would be a nice usability improvement.