Create a category that is just for you. Move those topics there. When you are ready, use then topic timer to publish those in public categories.
Someone will guide you to use PMs that you sent to yourself. But that is actually quite ackward way.
And no, we will not get more drafts because design is limiting drafts of new topics to one. You can have several post drafts as long those are in different topics.
Feature request for that is no go. It is requested so many times.