Going off personal experience, I’m not sure even that’s safe for me now…
To copy files from one project to another, you can use drag and drop. Create a new project via the New Project window–either using the novel template, if you like that, or blank, whatever you’re comfortable with. This is the project where you’ll move the chapter to so that it can expand at leisure.
Then, with that new project open, open your existing project. With the two project windows side by side, select the the documents you want to move from the current novel project and drag them into the binder of the new project. This will copy, rather than move, so if you really want them gone from the original project you’ll need to just move them to trash there by dragging them into the Trash container or selecting them and choosing Documents>Move to Trash (or clicking Shift-Delete).
Once you’ve copied files to a new project, there’s no link between the projects–they’re completely new files in that project, so changes you make there won’t affect the original project and vice versa. Most aspects will transfer with the files–references, keywords, snapshots, etc.–but label and status will not, and Scrivener links will not, as these depend on the specific project. You may not be using any of these at this point, so it might not matter to you, but it’s just something to know.
That said, Scrivener projects are designed to be able to hold a lot of work, so while creating a new project for this chapter is certainly a valid option, you could also just develop the structure in the binder of the existing project to accommodate its expansion. You can create new folders, nest documents anywhere, etc. Don’t feel limited by the set up of the Novel template–that’s just to get you started, but if you want to add a new root level folder (that is, at the same level as the Manuscript, Trash, and Research) you can do that; you could create a folder in Research that’s specifically just research files for this particular chapter; you could add a lot of note files as subdocuments to your chapter file in the Manuscript and just set them not to compile so they aren’t part of your final output but are easy for you to find and work with while writing. This is all going to be personal preference and just playing around to see what works, but plenty of authors use a single project to manage multiple books in a series, so it’s certainly possible to maintain everything in one project without splitting it out. (But then, plenty of people to create new projects for bits and pieces too, so again–up to you!)
EDIT: Oops, Ioa beat me. But in response to this bit:
That bug was fixed for 035, so you should be fine.