You can repost existing posts that have been published, scheduled or saved. To do so, just click on the post menu and find the Repost option. When clicking it, the composer will open with the content from the post you selected.
From the composer you might want to slightly modify the post, duplicate it to another page or publish/schedule it again for later.
You can also copy the post to another workspace or page by using the list view. Select list view, select posts, and then select "Duplicate". Afterwards, find the page / workspace you want the posts to be duplicated for the page selected.