You have the option to modify the existing subsidiary hierarchy. You have to accept the license agreement before you can modify the hierarchy.
Setup – Company – General Preference.

Specify a period during which authorized users can modify the subsidiary hierarchy. The maximum number of days is 30.
using Allow Subsidiary Hierarchy to be modified is the correct field to edit the structure of your subsidiaries.
When making changes to your Subsidiary Structure it is important to take note that this will have financial reporting impacts on your account. It is highly recommended to do the following:
- To ensure modifications are implemented correctly, make the modifications first in a Sandbox Environment
- Export Financial Statements and Consolidated Exchange Rates before making modifications
- Run Period End closing tasks, including Intercompany Elimination (if applicable)
- Check Roles and Permission Restrictions after making the modifications
- Check impact on customization and scripts
For more information, check SuiteAnswers ID: 91150 | Subsidiary Hierarchy Structure Modification