Can we update Child Account segment value to a Parent segment value?

Summary:

Can we update Child Account segment value to a Parent segment value?

Content (please ensure you mask any confidential information):

We have two Account segment values which has been defined as a Child value (Summary = No).
One of the accounts have no transactions or balances.
Second account includes a balance but has been transferred to another account. Now the balance of this second account is 0.00
Can we update these two accounts as Parent values please (Summary = Yes)?
Application allows us to update the Summary data field but I am trying to understand what implications we will have if we do this update.