I know how important to change the decimal separator in QuickBooks desktop, @EthylicCedric. Let me route you to the support that can help you change it to your preferences.

Since none of the steps provided above didn't work and still fails to change the separator, I recommend contacting our customer support to help you further into this matter. They have the right tools to access your account and initiate a screen sharing to view your screen and look for the cause of this issue. You can follow the steps below to reach us:

1. Open QuickBooks Desktop.
2. Go to the Help menu, then select QuickBooks Desktop Help/Contact Us.
3. Select Contact Us.
4. Provide a brief description of your concerns, then select Continue.
5. Sign in to your Intuit account, then select Continue, and click Continue with my account.
6. Enter the single-use code that will be sent to your email, then select Continue.
7. Select to chat with us or Have us call you.

Furthermore, I'll attach some helpful articles that you can visit if you want to manage your reports:

• How to run reports in QuickBooks Desktop.
• Customize reports in QuickBooks Desktop.

Let us know if you have other concerns about managing decimal separators or have any questions or inquiries about QuickBooks Desktop. The Community will be here and ready to lend you a hand.