Currently, we do not have an option to configure dark mode, belle.
QuickBooks Online will display its default light theme even if your iMac is set to dark mode. This is because QBO's web application is designed independently of your system’s appearance settings, so it will display as designed.
For the moment, you may consider using browser extensions that force dark themes on websites.
If you have any additional questions, please don’t hesitate to reach out. We're always here to assist you.