Summon a mob with a custom name duplicate the custom name but not the first {"text":""}

 /summon minecraft:cow ~ ~1 ~ {CustomName:"[

,{\"text\":\"100\",\"color\":\"green\"},{\"text\":\"❤\",\"color\":\"red\"},{\"text\":\" [Lv.2]\",\"color\":\"gold\"}]",CustomNameVisible:1,NoAI:1b}