You would not want to use someone else's creation in the form of G-code, as it can contain segments that are incompatible with your printer and could damage it.

When you slice the file in Cura and create G-code, it is a text file that can be manually edited to provide the necessary temperature changes. Any convenient text editor will work, but do not use a word processor such as MS Word or similar. You can use Notepad if you have windows or any of the many text editors that are available via the internet.

Do you have a reference document providing the necessary steps to determine the layer changes for placement of the temperature changes?