SELECT node.name, (COUNT(parent.name) - (sub_tree.depth +  1 )) AS depth
FROM nested_category AS node,
	nested_category AS parent,
	nested_category AS sub_parent,
	(
		SELECT node.name, (COUNT(parent.name) -  1 ) AS depth
		FROM nested_category AS node,
		nested_category AS parent
		WHERE node.lft BETWEEN parent.lft AND parent.rgt
		AND node.name = 'PORTABLE ELECTRONICS'
		GROUP BY node.name
		ORDER BY node.lft
	)AS sub_tree
WHERE node.lft BETWEEN parent.lft AND parent.rgt
	AND node.lft BETWEEN sub_parent.lft AND sub_parent.rgt
	AND sub_parent.name = sub_tree.name
GROUP BY node.name
ORDER BY node.lft;

ERROR:  колонка "node.lft" должна фигурировать в выражении GROUP BY или использоваться в агрегатной функции

select *
from
( -- здесь ваш запрос без order by
)
order by;