Search Layouts for Custom Objects Are Not Displayed and Cannot Be Edited

This issue occurs because a custom tab has not been created for the target custom object.
Follow these steps to create a custom tab and verify if the search layouts are displayed.

Operation Steps:

1. Navigate to Setup | User Interface | Tabs.

2. In the Custom Object Tabs section, click New.

3. Select the target custom object for Object, choose a Tab Style, and click Next.

4. Select the profile visibility settings and click Next.

5. Select the custom apps to include the tab and click Save.