Projectmanager Internal Link Code Location

Not 100% certain but you could check admin/dataset-form.php around line 92

<?php elseif ( 'project' == $form_field->type ) : echo $projectmanager->getDatasetCheckboxList($options['form_field_options'][$form_field->id], 'form_field['.$form_field->id.'][]', $meta_data[$form_field->id]); ?>

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