I'm happy to go over some steps for creating an expense account.
Here's how:
On your left panel, select Accounting.
Tap on Chart of Accounts.
On the right side beside Run Report, click the green colored box with New inside it.
A new prompt will pop up for a New account, select the Expense icon.
Fill in the necessary information needed for the expense account scroll down to see more boxes and details to be filled in.
Once done, click Save.
Once done saving, check your Chart of Accounts if the new expense category has been created successfully.
To help you manage your expenses in QuickBooks Online, check this write-up: Expenses and vendors. This will provide you links on how your expense transactions work in QuickBooks.
If you've created transactions and used the expense account, you should see it listed in a report. If this still isn't the case for you, I recommend trying some basic troubleshooting steps. Such as clearing the cache from your browser. Web browsers collect cache to save time when loading repetitive data and images. Over time these files can become outdated and corrupted, causing issues like the one with your account not showing in reports.
I'm including the link to clear the cache below. Please don't hesitate to let me know if you have any questions or concerns.