I can’t help on this issue, job expiry date should be controlled by admin.
Although you can display by filter hook.
function job_bm_filter_job_input_fields_extra($input_fields){
$meta_fields = $input_fields['meta_fields'];
// Add new fields in company tab , default meta group is company_info, job_info, salary_info, application
$company_info = $meta_fields['job_info']['meta_fields'];
$company_field_extra[] = array(
'meta_key'=>'job_bm_expire_date',
'css_class'=>'expire_date',
'required'=>'no', // (yes, no) is this field required.
'display'=>'yes', // (yes, no)
'title'=>__('Expiry date', 'job-board-manager'),
'option_details'=>__('Job expiry date', 'job-board-manager'),
'input_type'=>'date', // text, radio, checkbox, select,
'input_values'=> job_bm_get_date(), // could be array
);
$company_info = array_merge($company_info, $company_field_extra);
$input_fields['meta_fields']['job_info']['meta_fields'] = $company_info;
return $input_fields;
}
add_filter('job_bm_filter_job_input_fields','job_bm_filter_job_input_fields_extra');
Please see the documentation here
https://www.pickplugins.com/documentation/job-board-manager/filter-hooks/filters-job_bm_filter_job_input_fields/
Regards