Schema Builder for data model changes
Key Takeaway
Changes in Schema Builder are real metadata changes, but a new field isn't added to the page layout. To make the field appear on the record page, add it to the page layout, even when field-level security already makes it visible and editable.
Schema Builder is a visual, drag-and-drop tool in Setup for viewing and changing your org's data model: its objects, fields, and the relationships between them. You see and edit the whole schema on one canvas, so you don't have to click from page to page to find a relationship or add a custom field.
What Schema Builder shows
The canvas shows standard and custom objects with their fields, field values and required fields. The canvas also shows the lookup and master-detail relationships that connect the objects.
Schema Builder is enabled by default. You can use Schema Builder in all editions, in both Salesforce Classic and Lightning Experience.
In the left panel, you choose which objects appear on the canvas. For example, click "Clear All" and then select only the objects you want to see. Objects created outside Schema Builder, such as through an app or the API, don't appear on the canvas automatically. Select the checkbox for that object to show it.