We appreciate you for performing the steps provided by my colleague, Ana.

I'll be here adding help in fixing your issue with your customer list not staying in a Hierarchical view.

Beforehand, we'll need to create a backup to avoid losing any of your data. Then, we'll now be going to run repair tools for QuickBooks Desktop. 

Here's how:

1. Close first your QuickBooks.
2. Download the most recent version of QuickBooks Tool Hub, and save it where it can be located easily. If we've installed Tool Hub before, we can find out which version we have by just clicking the Home tab then it will show on the bottom.
3. Open the file we've downloaded (QuickBooksToolHub.exe). Next, we'll need to install and agree to the terms and conditions by following the on-screen steps.
4. To open the tool hub double-click the icon on our Windows desktop, when the installation finishes. (If you can't find the icon, do a search in Windows for QuickBooks Tool Hub and select the program).

Afterward, we'll need to Run Quick Fix my program, it'll run a quick repair and will shut down any background processes on your program. 

1. In the QuickBooks Tool Hub, select Program Problems
2. Select Quick Fix my Program.
3. Start QuickBooks Desktop and open your data file.

If the error still persists, Run the QuickBooks Install Diagnostic Tool this will fix common installation issues. 

1. Open the QuickBooks Tool Hub, then select Installation Issues.
2. Select QuickBooks Install Diagnostic Tool. Let the tool run. It can take up to 20 minutes.
3. When the tool finishes, restart your computer and start QuickBooks Desktop, then open your data file.
4. Update your QuickBooks to the latest release. This makes sure you have the most recent fixes and security updates.

Once done performing the steps, if the error in your customer's list still occurs. I recommend contacting QuickBooks Desktop support to help you point out the root cause of your issue and fix it.

Keep me posted if you have more questions about the customer list, providing assistance to you will be an honor. Have a blessed year!