Hi @JesusJohnSheila,
At this time, a night mode feature for QuickBooks Self-Employed (QBSE) isn't included in the software.
I believe it's a cool customization feature and would also like to add this to the product. With that said, we'll take note of this idea.
In case you have other questions concerning QBSE, you can take a look at this page: Get Started for QuickBooks Self-Employed. It's a web page that lists multiple articles for this product.
Feel free to utilize the comments section below if you have other queries. I'll be sure to get back to you.