Great to have you in the Community space, Edwin.

Adding numbers to your accounts from your Chart of Accounts (COA) won't affect the items posted outside of QuickBooks Online (QBO). It'll just update how your COA looks. 

If you wish to add an account number in your COA, you'll need to enable this option in your account. I'll show you how. 

1. Go to the Gear icon and select Account and settings.
2. Select the Advanced tab.
3. Click the Edit pencil icon in the Chart of accounts section.
4. Select Enable account numbers. 
5. Click Save and then Done.

Then to add your numbers in your COA:

1. Go to the Accounting menu and select Chart of accounts.
2. Select ✎ Batch edit above the Action column. 
3. Add account numbers in the Number column, and select Save once done. 

You can also check this link for more details about the process: Use account numbers in your chart of accounts.

In regards to modifying the order list of your COA, the option to do so isn't available in QBO. As a way around, you can look for a third-party app that has this feature. Just hover to the Apps menu and look for an app from there. You can also visit our QuickBooks Apps store for additional reference.

Additionally, you can also send your feedback to our product engineers. This way, they can review your suggestion and might consider adding this in the future updates. 

Once everything is in place, you might want to utilize this link for reference in matching your accounts flawlessly: Reconcile an account in QuickBooks Online.

If there's anything else you need assistance with about your COA or QuickBooks, you can always tag me in your reply. I'll be around to back you up!