Let me guide you on how you can create a sub-account for inventory and for fixed assets, Muhammad.
Sub-accounts are often used to help keep track of expenses when several activities are funded by the same account or the same sub-account. You can follow the steps below on how you can create a sub-account. To do so, I've outlined the steps below:
Go to the Gear icon ⚙ and select Chart of accounts.
Select New.
Select the account type and detail type. You can learn more about account types and detail types if you have questions.
Select Is sub-account and then enter the parent account.
Give your new subaccount a name. You can also add a description.
For the as-of-date, tell QuickBooks when you want your account to start. Then add the Balance to the account as of the date you choose.
Select a Default Tax Code. Note: Only some account types need this, like a bank, credit card, asset, and liability. If you need help, you can learn more about opening balances.