I typically create a new book for a new idea. I add all the entries immediately, which addresses Schnujo's NOT Doing NaNoWriMo'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