The Messages page offers the ability to filter by notifications or drafts of notifications created from the OneSignal dashboard

Create A Draft

Dashboard > Messages > New Message

A Draft is a Push Notification that you would like to save your progress on and are not ready to send. A draft can be created from the New Push form by saving the current form contents as a draft.

Completing a draft

A Draft can be edited/sent be filtering the Messages page by drafts and then selecting Edit on the draft

From here you can make edits to the draft just as you would a new message. Once you are happy with the notification you can select Confirm to send the message.

Or if you are still not ready to send the notification you can select Save as Draft to update the draft