Sorry, I'm not sure what exactly you're referring to. The "Manage Event Triggers" page does not have any checkboxes, though you can edit them to set some global options for certain event triggers.
The "Manage Events" page does have checkboxes, although if you are having problems saving that page please check the max_input_vars setting in php.ini. Make sure it's set to 100000 or higher, then restart Apache/PHP.