Add Custom Field on Entity Record to Address Subtab

To display a specific custom Entity field in the Address subtab of an Entity record, perform the following steps:

1.   Navigate to Customization > Lists, Records, & Fields > Entity Fields
2.   Click the desired field.
3.   Click Display
4.   Subtab: Select Main
5.   Click Save

To add the created custom field in the subtab,

1.   Navigate to Customization > Forms > Entry Forms
2.   Desired Entity form: Click Customize/Edit
3.   Click Move Elements Between Subtabs
4.   Click Fields
5.   Click Main
6.   Locate the custom field created
7.   Enter Checkmark in Select column for that custom field
8.     Subtab: Select Address
9.   Click Save
10.   Click Save