UPDATE subscribes SET feed = JSON_SET(feed, '$[0]', 100)

  SELECT aa.id, aa.email, JSONB_AGG(bb.*) AS child
  FROM "Users" aa
  LEFT JOIN LATERAL (
    SELECT b1.id, b1.email, JSONB_AGG(cc.*) AS child FROM "Users" b1
    LEFT JOIN LATERAL (
      SELECT c1.id, c1.email, JSONB_AGG(dd.*) AS child FROM "Users" c1
      LEFT JOIN LATERAL (
        SELECT d1.id, d1.email FROM "Users" d1 WHERE d1."parentId" = c1.id
      ) dd ON true
      WHERE c1."parentId" = b1.id
      GROUP BY c1.id
    ) cc ON true
    WHERE b1."parentId" = aa.id
    GROUP BY b1.id
  ) bb ON true
  WHERE aa."parentId" IS NULL
  GROUP by aa.id

UPDATE subscribes SET feed = JSON_SET(feed, '$[0]', 100)