This function adds a 'Year' dropdown that will display any year you have registration in, you can select the year and view registrations specifically for that year.

example.php

<?php //Please do not include the opening PHP tag if you already have one.

// Adds a 'year' filter to the registration admin list table.
add_filter('FHEE__Extend_EE_Registrations_List_Table__filters', 'tw_ee_add_year_filter_to_reg_list_table', 10, 3);
function tw_ee_add_year_filter_to_reg_list_table( $filters, $list_table_object, $screen ) {
    $where = array();
    
    //Check if we have a current reg_status set.
    if(! empty( EE_Registry::instance()->REQ->get('_reg_status') ) ) {
        $where['STS_ID'] = EE_Registry::instance()->REQ->get('_reg_status');
    }
    
    //Check if we are looking for a specific category
    $cur_category = EE_Registry::instance()->REQ->get('EVT_CAT');
    
    if ($cur_category > 0) {
        $where['Event.Term_Taxonomy.term_id'] = $cur_category;
    }
    
    //Build out the query to pull the years you have registrations for.
    $query_params[0] = $where;
    $query_params['group_by'] = array('reg_year');
    $query_params['order_by'] = array('REG_date' => 'DESC');
    $columns_to_select = array(
        'reg_year' => array('YEAR(REG_date)', '%s'),
    );
    $regdtts = EEM_Registration::instance()->get_all_wpdb_results($query_params, OBJECT, $columns_to_select);

    // setup vals for select input helper
    $options = array(
        0 => array(
            'text' => __('Select a Year', 'event_espresso'),
            'id' => ''
            )
        );

    foreach ($regdtts as $regdtt) {
        $year = $regdtt->reg_year;
        $options[] = array(
            'text' => $year,
            'id' => $year
            );
    }
    
    //Add the new 'Year' dropdown to the available filters.
    $filters[] = EEH_Form_Fields::select_input('year_range', $options, EE_Registry::instance()->REQ->get('year_range'), '', 'wide');

    return $filters;
}


add_filter('FHEE__Registrations_Admin_Page___get_where_conditions_for_registrations_query', 'tw_ee_reg_list_table_year_where', 10, 2);
function tw_ee_reg_list_table_year_where( $where, $request ) {
    //Check we have a year set to filter on the request.
    if( !empty( $request['year_range'] ) ) {
        
        //Sanatize the input.
        $year_requested = sanitize_text_field($request['year_range']);
        
        //Build out the query using the Janurary 1st - 31st December based o the current year selected.
        $where['REG_date'] = array(
            'BETWEEN',
            array(
                EEM_Registration::instance()->convert_datetime_for_query(
                    'REG_date',
                    $year_requested . '-01-01 00:00:00',
                    'Y-m-d H:i:s'
                ),
                EEM_Registration::instance()->convert_datetime_for_query(
                    'REG_date',
                    $year_requested . '-12-31 23:59:59',
                    'Y-m-d H:i:s'
                ),
            ),
        );
    }

    return $where;
}