Always make sure to backup the Knowage database. All objects' schema are stored in the database. You can find the name of the database and it's credentials in the server.xml file. If you are using the community edition, it will be either be knowage_ce or knowage_demo depending on the charting tool that was installed .
If anything goes wrong or if you need to migrate your database to a new environment / server, you can simply restore the database and everything you worked on will be there.