To backup all or multiple databases on the same server please follow the following steps.
Make sure you have all the requirements listed here Database Backup Using SSH Server
Turn ON Use Our Public Key? or Use Your Private Key? toggle on database integration
You will see a toggle for Multi-Database User? turn that ON.
Keep the Database Name field empty
Save integration and click on create node button.
On the node creation screen, you will be able to select multiple databases or backup all databases.