@AmolShah @GavinCrump Thanks very much for your help, I hope it is useful for the community for future if needed.
I am forced to learn Python because a script originally done with nodes, it crashes literally the computer and switches off and with python can be simplified quite a lot, and I am not a programmer.
My question as others are quite basic but the final script is more complex, so having simple examples I can try to develop more by myself.
The question is looking to achieve the following challenge: Python. Add a sublist that starts with a word to the following sublists and repeat from each time a sublist starts with word appears