private function mergeFormConfig(array $parentConfig, array $childConfig)
    {
        // save the fields config for later processing
        $parentFields = $parentConfig['fields'] ?? [];
        $childFields = $childConfig['fields'] ?? [];
        $removedFieldNames = $this->getRemovedFieldNames($childFields);

        // first, perform a recursive replace to merge both configs
        $mergedConfig = \array_replace_recursive($parentConfig, $childConfig);

        // merge the config of each field individually
        $mergedFields = [];
        foreach ($parentFields as $parentFieldName => $parentFieldConfig) {
            if (isset($parentFieldConfig['property']) && \in_array($parentFieldConfig['property'], $removedFieldNames)) {
                continue;
            }

            if (!isset($parentFieldConfig['property'])) {
                // this isn't a regular form field but a special design element (group, section, divider); add it
                $mergedFields[$parentFieldName] = $parentFieldConfig;
                continue;
            }

            $childFieldConfig = $this->findFieldConfigByProperty($childFields, $parentFieldConfig['property']) ?: [];
            $mergedFields[$parentFieldName] = \array_replace_recursive($parentFieldConfig, $childFieldConfig);
        }

        // add back the fields that are defined in child config but not in parent config
        foreach ($childFields as $childFieldName => $childFieldConfig) {
            $isFormDesignElement = !isset($childFieldConfig['property']);
            $isNotRemovedField = isset($childFieldConfig['property']) && 0 !== \strpos($childFieldConfig['property'], '-');
            $isNotAlreadyIncluded = isset($childFieldConfig['property']) && !\array_key_exists($childFieldConfig['property'], $mergedFields);

            if ($isFormDesignElement || ($isNotRemovedField && $isNotAlreadyIncluded)) {
                $mergedFields[$childFieldName] = $childFieldConfig;
            }
        }

        // finally, copy the processed field config into the merged config
        $mergedConfig['fields'] = $mergedFields;

        return $mergedConfig;
    }