I added a new account in the chart of accounts but it's not showing. I tried adding it again but it says that I already have an account with the same name. What can I do?

I can share some information about adding new accounts in QuickBooks Online (QBO), @nabatman-ye-gmai. 

The error you're having with the subaccounts may be caused by the piled-up cache in your regular browser. A regular browser's cache stores temporary internet files from your browsing history. However, as it collects too many files, this may cause performance issues in your account.

I've got some steps to help fix this issue. First, you'll have to sign in to your QBO account using a private browser. This helps isolate the issue since it doesn’t store data in the cache. Here are the following keyboard shortcuts: 

• Safari: Command + Shift + N
• Mozilla Firefox: CTRL + Shift + P
• Google Chrome: CTRL + Shift + N 
• Microsoft Edge:  CTRL + Shift + P

If it works, here's how to clear cache and cookies to fix issues when using QuickBooks Online. Restart your browser right after. 

You can also try to log in to your account using other supported browsers (Firefox, Google Chrome, Safari, Microsoft Edge) if the steps above didn’t work.

You can have as many subaccounts under a parent account in your Chart of Accounts up to 4 levels deep. For more information about adding subaccounts and on how it will look in your Chart of Accounts tab and reports, refer to the following article: Create subaccounts in your chart of accounts in QuickBooks Online.

Additionally, I'd recommend checking out this article to learn more about the chart of accounts in QBO: Learn about the chart of accounts in QuickBooks. It includes a detailed breakdown of account types and their definitions.

Please don't hesitate to leave a reply below if you still have questions about your chart of accounts. I'm always here to assist. Keep safe and have a great rest of the day!