This would be similar to an email draft: You can start writing the market, but if you close out of the page, it will be saved for you to pick up later, and you can either finish the draft and publish the question, or delete the draft. Currently, Manifold does something similar as an anti-frustration feature, so that you don't lose what you've written if you click a link or back button, or realize that you're making the wrong market type. If you are in the process of creating a question and leave, the next time you go to create a question, the title, description, and options (if it was free response or MC) will still be there. However, it would be useful to be able to save multiple drafts instead of just one, or to save a draft and then create a different question (Manifold's current feature doesn't let you create a new question without destroying the saved data from the old one).

This feature could be very helpful when creating a market that has complicated resolution criteria - that way you wouldn't need to write the whole thing in one sitting or use an external program to save your draft. It could also be used as a feature where you can show other users your draft so that they can make suggestions on how to improve the resolution criteria, but that ability is not required for this to resolve YES.

I opened a thread in the suggestions Discord about this: https://discord.com/channels/915138780216823849/1144464431925956758