Tabit supports dark mode relying on the operating system preference. You have to set your operating system to dark mode/theme to activate it.
Windows 10 Dark Theme
Windows 10 has introduced a new dark theme that covers various shades of black in the background, pop-up dialogs, file explorer, context menus, and so on.
To access Dark mode, click on the Start button and select Settings, which is the gear icon, or press the WIN+I keys together.
On the Personalization page, select Colors, and select the Dark option under the Choose your color section.
Macos Dark Theme
Here are the steps for turning on the Dark mode on macOS Mojave or newer.
Open the Apple menu in the top left corner of your screen and select System Preferences.
Pick the General tab.
Select Dark theme from the two options in the Appearance section.