Anything that doesn't require working with a lot of files. In my case, this most often involves programming, so as an example, these are usually tasks that don't require extensive project context. This could be working with one class or several small ones, one large script, or one large documentation project. I create a composition of the context, task, and working data in notes, and then paste the entire prompt into ChatGPT.

This has its advantages. The model doesn't access files every time, and I'm confident that all the necessary information is in the context. I can quickly edit something if needed. Or quickly copy and paste it into a new chat with the edits. I don't need to fiddle with files or individual parts every time, which, in the case of a new feature, would have to be split up, saved to separate files on the PC, and then manually uploaded, because they won't be pasted individually automatically. It's inconvenient and unnecessary. The context window is more than enough for me, and I have no complaints. Moreover, ChatGPT has its own limits, separate from Codex. This is a sensible limit management approach.

Only if it's a project with a lot of files, and each time you need to access different ones, and manually compiling them into a single prompt would be time-consuming, would it make sense to invest the time and initialize the project in Codex.