Hello~ I'm looking for a manga where the main lead wakes up to find themselves in a child's body but still retain all their previous memories which makes them very smart. Something like Tensei shi chatta yo I guess. I don't mind if it's reincarnation or a novel. Thank you!

How about these
Hiraheishi wa Kako o Yumemiru
Kouritsu Kuriya Madoushi, Daini no Jinsei de Madou o Kiwameru
Tsuyokute New Saga

Mujaki no Rakuen