What is the Series Codex?
The series codex is the same as the standard codex, with the additional bonus of the entries being shared over every book in the series. This saves you having to make the same entry over and over!
How do I move a codex entry to the series codex?
To move your codex entry between the book and series codex:
Open up the codex entry
Click on the action menu
Select move to series/move to book.
How can I view codex entries in my book vs codex entries in the series?
There are handy tabs in the codex panel for you to view all the codex entries associated with the book (all), the codex entries associated with the series (series), and the codex entries only associated with that book (book).
I want to make entries that go straight to the series codex; how do I do this?
To add a codex entry to the series codex upon creation:
Go to the series codex tab
Create your codex entry
At the top of the codex entry, there is a message saying that the codex entry will be part of the book series.