Basically, think of it as the end of ROM.
Add at the end of ROM.
Because of the structure of the song, it is divided into multiple pieces of data, so it can not be said that it is definitely only the end of the ROM.
However, I think most of it has been added to the end of ROM.
If you really want to know the change point, save it in a different name with “Menu -> Save as” and take the binary diff.
Several tools have been developed that can get diff in binary format.
I often use software called WinMergeU and stirling.