Index button is a feature that you can use to add a new action button on the top of the module.

Available Key

NameDesc
labelThis key is used to provide naming the button label
iconThis key is used to provide an icon on the button, you can use FontAwesome
urlThis key is used URL that will be addressed when the user presses the button

Example 

$this->index_button[] = ["label"=>"Print Report","icon"=>"fa fa-print","url"=>CRUDBooster::mainpath('print-report')];

Tips : 

CRUDBooster :: mainpath () is inherited from CRUDBooster helper to generate Base URL of the relevant module.