Yes. You can close an investment account in the app once the balance is $0 and there are no pending deposits or withdrawals.
How to Close an Investment Account
Withdraw all funds from the account.
Wait for the withdrawal to fully process. The account must show a $0 balance with no transactions in progress.
Open the account you want to close.
Tap the menu icon in the top-right corner.
Select Close account.
What Happens After You Close an Account
Closed accounts remain visible in your records for reporting and tax purposes.