Display Customize View Button for Child Record Sub-tab in Edit Mode

In the case user has created a child record and added to parent record's tab, the Customize View button is displayed only in View mode and it isn't displayed in Edit mode, the following steps should be done:

1. Navigate to Customization > Lists, Records, & Fields > Record Types > Click on a record set as child

2. Records are Ordered = unchecked

3. Allow Child Record Editing = unchecked

4. Click Save

Note: However the steps provided above will disable adding of child records in Edit mode directly from parent record.

More information about Parent/Child records can be found under SuiteAnswers article 10149: Using Child Records.