The Artscroll siddur offers two insertions that one can add to the bracha of shma koleinu every day, one asking forgiveness for sin and the other asking for livelihood. What are the sources for these insertions, and why are they not found in the Koren, Metzudah, or Rinat Yisrael siddurim?
I have noted that these additions are not included in any nusach Ashkenaz siddurim I have seen, while they are included in every nusach Sefard siddur I have seen. If they are included in the nusach Ashkenaz Artscroll siddur, it might be out of a desire for some conformity and unity between that and their Sefard siddur. Unfortunately, I have no source, and this is purely speculative.
The Magen Avraham in O.C. 119:1 quotes from the Sefer Hakavanos that it is a good thing to say these two prayers in Shema Koleinu. He additionally sources the Zohar Shemos 109-110. The Mishna Berura (119:4) cites this Magen Avraham as halacha. Artscroll often inserts additions based upon the advice of the Mishna Berura, as you will find in other places in the Artscroll siddur (Parts of the Korbanos section, for example).