I have a planning "novel" where I have developed all of my story arcs in snippets, and it also has the codex I use for all of my novels. I was starting a new book and wanted to use the planning book as the template so I could have all of the snippets (I planned on removing the ones I no longer needed). I tried it several times and that dog won't hunt. It never returns from the create novel function. I even went and watched Project Hail Mary and it was not done, so that was over 4 hours. I selected create a novel, use template, the planning "novel", and options codex and snippets only. I have 810 codex entries and 162 snippets. A handful of the snippets are huge - they have the prose of two other novels, so 136K words and 104K words. There is no way to import all of the snippets but if I uncheck the snippets, it seems to work.