If you want to prepare a new post without publishing it right away and you have editor permissions for a channel, you can create a new draft. Drafts are only visible and publishable by channel editors and owner. Additionally, all the comments in the draft will be removed once the draft is published. This way you can use the comments section to have a discussion about the draft before publishing.
Adding a draft works the same way as creating a new post but instead of clicking share, click the arrow from the top right corner of the new post and select "Save as draft".
Once you save a post as a draft, the drafts section will load automatically (unless manually hidden) and show all the drafts in that channel. From here you can publish the draft when it's time.