While it isn't possible to overwrite an existing account on your COA, you can import the missing account in QuickBooks.
Before proceeding, here are the lists of file requirements for import:
The file size limit is 2 MB or 1000 rows per import. If the file is larger, you can do multiple smaller imports.
The file must be in Excel or CSV format and must have AccountType and Name fields. You can download the sample file for your guidance.
You can import sub-accounts by using the parent account name, followed by a colon (for example parent:sub-account).
Account numbers should not be left blank and should not include decimal points.
All columns must have headings, even if the column is empty or has no date.
Let me guide you through the process of transferring your account:
Click the Gear ⚙︎ icon at the top.
Select Import Data under Tools.
Select Charts of Accounts.
On the Import accounts page, click the Browse button.
Find the Excel file to import, then select Open.
Click Next to continue.
Map your data, then click Next.
The next page shows the accounts that are ready to be imported.
Adjust your data if necessary, then click Import.
You can also transfer other existing data on your new account to help you having to set up the items from your lists one by one. Check this out for the detailed steps and additional information: Move your Lists to QuickBooks Online.
Let me know if you need assistance and I'd be glad to lend a hand.