You can personalize the graphical user interface to better suit your needs or style.
For example, you can reorganize the menu bar, can create, delete, or modify toolbars, and many more.
The changes are stored in a configuration file in your Chemaxon user folder under the version number which the customization was made with.
Please make sure that your configuration.xml file is copied under the new version number folder when you update your MarvinSketch.
The default settings can be restored by deleting the configuration file.
For more information on configuration and the configuration file please consult this section of the Developer's Guide.