sorry for my late reply,
I changed my code the following… (If you have any suggestions for multifile uploads, please let me know) Thank you.
if ( 'upload_receipt' === $current_section ) {
return array(
array(
'type' => 'title',
'id' => 'upload_receipt_settings_section',
),
array(
'title' => __("Payment methods",$this->td),
'desc' => __("Select Payment methods you wish to activate receipt uploading feature", $this->td),
'id' => 'peprobacsru_allowed_gatewawys',
'default' => 'bacs',
'type' => 'multiselect',
'class' => 'wc-enhanced-select',
'css' => 'min-width: 400px;',
//'options' => $this->get_wc_gateways(),
// 'custom_attributes' => array(
// 'multiple' => 'multiple',
'options' => array (
'bacs' => 'bacs',
'cheque' => 'cheque',
'alg_custom_gateway_1' => 'alg_custom_gateway_1',
)
),