Thanks for your offer to help MrToucan.
What I have done so far:
Downloaded the 5e Spells Mod, the Expansion Mod as well as the corresponding script file. I have placed the .pak files into the Mod folder along with the script file which is also a .pak file. From there I opened the BG3ModManager program which showed the 2 Mods and said that the script file needed to be added. I tried to use the Export to Order button but nothing seems to have happened.