Hi Gabriel,
How are you?
Certainly I'm having some trouble in finding the "where and when" to place relations in the forms. (it is making me sweat :-) )
Your solution is indeed cleaner.
However once you are in the chapters editing form, you can edit any of the existing records, but if you hit the New button, it creates an orphan chapter in the chapters relation, as it does not have reference to any book_id.
In my solution, in the List_Chapters form I have the book id and I pass it to the Chapter_CRUD form through : chapter.book_id that it the book_id in the chapters relation (the relation field in the chapters relation that binds records from that table to the book relation)

I believe that there should be another solution, perhaps not so different from what I've done, probably simpler, that allows this whole cicle.
The remaining problem to make it work:
In the last step, while in the chapter editing form, I can edit the chapter, but I can't pass the book id to create the new chapter, and I have to select it manually from the relationship field.
The problem is that I find no option to do a similar thing as "Use as default on opened form" that is available when you open a form from the list, but not when you open the same form from the New button.
So in the end the question would be how to make the New button aware of the current book_id, instead of having to select it from the relation field.
This is the Form when I arrive from the chapter list:

This is the same Form when I arrive from the New button in the Form:

This is the same Form after I select the book in order to create a new chapter for the book.

If I do all this complicated flow, I end creating a chapter for the book.
Well, I know I can achieve the same if I divide the operation in small pieces and ask the user to create a book, and the on another form select the book and create the chapter. Simpler, YES, user friendly, not so much, because if the user is checking the chapters and wants to create a new one, it has to exit the form, enter another form, search for the book and then create the chapter, when he was already there in the moment decided to add the new chapter.
Anyway, I apprecitate your comments! And certainly will remember them when creating future artifacts.
If you have an idea of how I could achieve passing the book_id to the New button, please let me know.
On a different topic ... I have requested the licence through the form in your page, but I haven't received any answer yet.
I'll appreciate if you could check the request arrived correctly.
Thank you very much!
Warm regards
Ricardo