Can I back up my quickbooks online company file and convert it to a desktop file so I can access it if needed? My intention is to start a new company file from scratch.

You can use the following reference

https://quickbooks.intuit.com/learn-support/en-us/import-or-export-data-files/export-and-convert-you...

You can use the trial version of QB Desktop to access your historical data for good.

We offer ways for you to access your QuickBooks Online (QBO) company file to help you start a new one, Robert. We'll gladly discuss the processes below.

You can back up your QBO company file if subscribed to the Advanced plan. If not, QuickBooks will automatically save your data, so you don't need to worry about it. 

On the other hand, you can also opt to perform any of the following to save your company file:

• Move your data to QuickBooks Desktop (QBDT) by using a trial version
• Export data out of QBO

After that, you can cancel your current QBO company and start a new one. To do this, here's how:

1. Sign up for QuickBooks Online.
2. Enter your user ID and password. You can use the same user ID and password as before.
3. Optional: If your previous company had payroll, add Payroll in Step 2 of the sign-up process.

Once done, import your lists (vendors, customers, inventory, and chart of accounts) to your new QBO company.

Additionally, QuickBooks offers a range of financial reports that can provide an overview of your business. To run, customize, and print one, you can refer to this article: Pull up reports in QuickBooks Online.

Don't hesitate to comment below if you have questions about backing up your company file and creating a new one in QBO. We're always here to help you out. Have a great day.