You can save the render settings using the Save icon next to "User settings" render quality. But they cannot be made default. (because when you make a test render, you don't want to use these settings, but faster ones). As for the Corn items, you should have a corn icon at the bottom of your collections. Long click it, and if you have a "ghost" icon, choose it, it will permentently hide the Corn items. If you don't have this icon, look for all the files that start with a double tilde ~~ in your Vue content folder, and delete them.