EASA definition of Major Mod - where?
In FAA land, it is FAR 43 Appendix A.
Does EASA have a similar definition?
I have seen some spectacular cases lately where a mod on a Euro-reg plane got turned down by EASA, but the proper way to have approached that job would have been to check whether it is a Major Mod at all; if not, the paperwork should be doable locally. One should not invent major mods unless the proposed work is explicitly on some major mod list.