How to install this feature or improvement:

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-Add "to user_bulk_action_form" function from "user_bulk_forms" file, this lines for add the new option (enrol multiple users at multiple courses)

context:

Before:   

        $actions[4] = get_string('displayonpage');
        if (has_capability('moodle/user:update', $syscontext)) {
            $actions[5] = get_string('download', 'admin');
        }	
        $objs = array();
        $objs[] =& $mform->createElement('select', 'action', null, $actions);
        $objs[] =& $mform->createElement('submit', 'doaction', get_string('go'));
        $mform->addElement('group', 'actionsgrp', get_string('withselectedusers'), $objs, ' ', false);

After:
		
        $actions[4] = get_string('displayonpage');
        if (has_capability('moodle/user:update', $syscontext)) {
            $actions[5] = get_string('download', 'admin');
        }
        if (has_capability('moodle/user:multienrol', $syscontext)){
        	$actions[6] = get_string('enrolmultipleusers', 'admin');	
        }		
        $objs = array();
        $objs[] =& $mform->createElement('select', 'action', null, $actions);
        $objs[] =& $mform->createElement('submit', 'doaction', get_string('go'));
        $mform->addElement('group', 'actionsgrp', get_string('withselectedusers'), $objs, ' ', false);

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-On "user_bulk.php" 
add: case 6: redirect($CFG->wwwroot.'/'.$CFG->admin.'/user/user_bulk_enrol.php');

context:

Before:
    switch ($data->action) {
        case 1: redirect($CFG->wwwroot.'/'.$CFG->admin.'/user/user_bulk_confirm.php');
        case 2: redirect($CFG->wwwroot.'/'.$CFG->admin.'/user/user_bulk_message.php');
        case 3: redirect($CFG->wwwroot.'/'.$CFG->admin.'/user/user_bulk_delete.php');
        case 4: redirect($CFG->wwwroot.'/'.$CFG->admin.'/user/user_bulk_display.php');
        case 5: redirect($CFG->wwwroot.'/'.$CFG->admin.'/user/user_bulk_download.php');
    }

After:
    switch ($data->action) {
        case 1: redirect($CFG->wwwroot.'/'.$CFG->admin.'/user/user_bulk_confirm.php');
        case 2: redirect($CFG->wwwroot.'/'.$CFG->admin.'/user/user_bulk_message.php');
        case 3: redirect($CFG->wwwroot.'/'.$CFG->admin.'/user/user_bulk_delete.php');
        case 4: redirect($CFG->wwwroot.'/'.$CFG->admin.'/user/user_bulk_display.php');
        case 5: redirect($CFG->wwwroot.'/'.$CFG->admin.'/user/user_bulk_download.php');
        case 6: redirect($CFG->wwwroot.'/'.$CFG->admin.'/user/user_bulk_enrol.php');
    }

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-Add to admin.php ( in my case: "moodle\lang\en_utf8" ) the next line:

$string['enrolmultipleusers'] = 'Enrol the users';

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-Add a new capability to database:

INSERT INTO `moodle`.`mdl_role_capabilities` (
`id` ,
`contextid` ,
`roleid` ,
`capability` ,
`permission` ,
`timemodified` ,
`modifierid`
)
VALUES (
NULL , '1', '1', 'moodle/user:multienrol', '1', '0', '0'
);

New capability to admin role, for be able to enrol multiple users to multiple courses

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- Add the file "user_bulk_enrol.php" to "/admin/user/"

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Ready for use 

;)