Does thei individual legislator have a specific particularizex harm or invaded right that can be addressed by the courts? Yes. He as a legislator has the right under the constitution to propose, debate and vote on regulations for the conduct of elections. That right was denied him in particular.
I'd extend it to say that any legislator who was in the chamber in 2018 and 2022 when the laws were passed has a right to sue because the bill they voted on and passed is now being overturned unconstitutionally.
Or, more to the point, the vote they passed via constitutional authority is being replaced by ballot initiatives that don't have constitutional authority for the subject matter, which harms the legislator's ability to exercise their plenary power.
-PJ