Q. Since you may ask all your needs on shomea tefila in SE, why can you not answer Yehe Shme Rabba, it is a tefilah after all?

A. Toldos Zeev (Brochos 21b) indeed opines that one can answer yehei shmei rabba in the middle of the brocho of shomea tefila. He maintains it is a logical kal vachomer, if you can ask for all your private needs then, why not daven for Kvod Shomaim or Hashem’s honor too. He carries further this argument against others who disagree with him, arguing that there is a difference between praying for human necessities, which was the intention of the brocho, and Heavenly requirements that were not included.
Eishel Arohom (Butchatch 104: 7) maintains that since our Sages instituted not to answer kadish in the middle of the amida, in order to avoid confusion, they included the complete amida covering shomea tefila too.
Afikei Meginim (119: biurim 2), similarly expresses that from words of the Talmud and Poskim there seems to be no exclusions to the ruling of not answering kadish during all sehmone essrei. He explains that yehei shmei rabba is more that a prayer, it is a most important, crucial and elevated declaration, and that in itself creates a hefsek that is prohibited in the middle of the amida.
Horav Shlomo Miller’s Shlit’a opinion is similar.

Rabbi A. Bartfeld as advised by Horav Shlomo Miller Shlit’a