The first thing you will want to do is hide some of your database objects so that they do not show up in the top-level of the Relational Navigation View.
Your first approach should be to consider whether the user or group of users should have access to the objects at all. It is best to configure your security so that users do not have read permissions to database objects that you do not want them to see. This makes your database more secure and allows you to configure on a group-by-group basis who gets certain permissions.
Limiting the visibilityof your database objects using database security will also improve load times for Gatsby Database Explorer since there will be fewer items that it will need to analyze during startup.
Only after you have your security configured properly should you consider hiding a database object. Hiding it makes it unavailable to all users from the top-level of the Relational Navigation View, but the object may appear elsewhere if it participates in a relationship.
To show or hide particular database objects using the Gatsby Design Assistant, open your data sources file using in the Design Assistant and select your database. Click "Properties...". Select the Views tab. From the Views tab right-mouse click on the object. This will bring up a context menu with an item called "Show". To hide the item, uncheck "Show". Alternatively you can select the item and click "Properties...". This will bring up the property page for the object. Set the "Show" option on the "General" tab of the property page to indicate whether you want the object to be shown or hidden.
For Microsoft Access databases, objects can be hidden using Microsoft Access. To hide an object in Microsoft Access, right-mouse click on the object and select "Properties...". There is a check-box in the Properties tab that determines whether or not the object is hidden. You can display hidden objects in Access by selecting Options from the Tools menu, going to the view tab, and checking hidden objects. For Microsoft Access databases, only Table objects can be hidden using the Gatsby Design Assistant.