Copy-pasting blocks can be a powerful way of re-using a layout again, either on the same page or by moving it to another page. Especially if you only want to clone a part of the page and not the entire page.
To copy a block, select it in the editor. Selecting the uppermost block in a hierarchy will automatically select all child blocks.
From the toolbar, click on the More Options button to see a range of extra block options. From the dropdown that appears, select Copy.
This will copy the selected block(s) to your clipboard.
Now navigate to where you want to insert your block. This could be on the same page or another page. From an empty line simply paste in your block content by using the keyboard shortcut
Ctrl + V (PC) or
Cmd + V (Mac). Your block will now be ready for you to edit.