Welcome, @David1551.
It's nice to have you in the Community. I can help walk you through adding or modifying a parent category/account in QuickBooks Online (QBO).
To start off, a category is a way of classifying the products and services you sell to customers to make accounting for inventory easier. Just to confirm, are you trying to add/modify accounts in the Chart of Accounts? If so, here's how to do it:
1. Go to the Gear icon at the top and pick Chart of Accounts under Your Company column.
2. Locate the account that you want to change, then on the Action drop-down, select Edit.
3. Click the Account Type drop-down and choose a new account, then Save and close.
As a reference, you can also check out this article for further guidance: How to change the type of an existing parent account or sub-account.
That's it! Please let me know how it goes or if you're referring to something else in the comment section below.