I typically create a new book for a new idea. I add all the entries immediately, which addresses Schnujo's problem of entries being in the wrong order if you do them out of order. You can't leave them blank, so I just populate them all with a brief placeholder (my signature, like below.) Then on the day I work on the assignment, I fill in the entry. Many of them say "see Google Drive" - for example, I use spreadsheets for lists and character profiles.

But I often do the actual work of the assignment offline, in a traditional paper notebook or in Samsung Notes on my phone, and then I type them up later or copy/paste them into the WDC book entry.

Cheers,
Michelle