Not all field properties appear in the entity type edit form

This is a minor improvement.

The fix is straightforward.
In sparql_entity_storage module, in sparql_entity_storage_form_alter there is the following code:

foreach ($base_fields as $field_name => $base_field) {
    // The entity id doesn't need a mapping as it's the subject of the triple.
    if ($field_name === $id_key) {
      continue;
    }
    $columns = $base_field->getColumns();
    foreach ($columns as $column_name => $column) {
      $title = $base_field->getLabel();
      if (count($columns) > 1) {
        $title .= ' (' . $column_name . ')';
      }

      $form['sparql_entity_storage']['base_fields_mapping'][$field_name] = [
        '#type' => 'details',
        '#title' => $title,
        '#description' => $base_field->getDescription(),
      ];

      $has_mapping = $mapping && $mapping->getMapping($field_name, $column_name);
      $form['sparql_entity_storage']['base_fields_mapping'][$field_name][$column_name]['predicate'] = [

As it is quite clear by the code itself, the 'details' fieldset is built for each column mainly overriding the previous property, thus only the last property shown.