Who Composed the Prayer Nishmat Kol Chai?

Greetings, There are several opinions regarding the identity of the composer of the prayer Nishmat Kol Chai: Some say that this prayer was instituted by the Men of the Great Assembly (see Rashi in Sefer HaOra, Part 2, end of Siman 46, and his student Rabbeinu Simcha in the Machzor Vitri, Hilchot Pesach, end of Siman 74, as well as the Mordechai in Pesachim in "Seder Bekitzra" under Arba). For further reference, see LeChid"a in Sefer Tov Ayin, Siman 18, Oth 30. In the Sefer Avudraham (Seder Shacharit of Shabbat and its explanation), it is written that some say the sage who composed Nishmat Kol Chai was named Yitzchak and his wife was Rivka; they composed it in honor of our forefather Yitzchak and our mother Rivka, so as to remind us of their merit. A third and fourth opinion were found in the siddur "Seder Avodat Yisrael" (page 206), where it states: "I found in an old commentary around a siddur manuscript from the year 1407, according to the custom of Troyes, the following: I heard from Rabbi Yehuda bar Yaakov that Rabbi Shimon ben Kefa established Nishmat Kol Chai." End of quote. In another commentary, I found this wording: Shimon ben Kefa, and some say Shimon ben Shetach, established Nishmat Kol Chai, and his name is hinted at in reverse, that is: Sh - Shoken Ad, M - Mi Yedameh, A - Ad Hineh Azrono, V - Veilu Pinu, N - Nishmat. With blessings, Hillel Meirs