Simplified variant of 幺?
幺 is used formally in the PRC, as in 幺女, 幺妹, 幺三五, meaning "one" or "youngest".

Therefore, it is part of the simplified script, but it was never simplified to begin with. It is a standard character. 说文 says: 小也。通俗文曰。不長曰幺。細小曰麼。許無麼字。象子初生之形。子初生，甚小也。俗謂一爲幺。亦謂晚生子爲幺。皆謂其小也。於堯切。二部。凡幺之屬皆从幺。

康熙字典 also describes this character, and adds at the very end: 俗作么

么 is therefore an 异体字 that seems to have been normalized within the traditional script, at least as it is used in Taiwan and other locations. It is also used in China, though, as in 么妹. 么 in China is of course the interrogative particles "me" or "ma" in its own right.

It is 么麼 in traditional, but 幺麽 (or even 幺么) in simplified.

This is gonna bake your noodle further: note how the traditional 么 is part of the simplified 麽, whereas the simplified 幺 is part of the traditional 麼.