Dashboard, a longtime Mac feature that Apple has been phasing out for the last few years, has been eliminated in macOS Catalina and it is no longer available for use.
The Dashboard option, first introduced in OS X 10.4 Tiger, used to be a prominent Mac feature, housing sticky notes, a weather interface, a clock, a calculator, and other customizable widgets.
It was disabled by default starting in macOS 10.10 Yosemite, and in the current version of macOS, Mojave, it’s still disabled unless you seek it out, enabling it as part of Mission Control or adding it to the Dock.
In Catalina, there is no more Dashboard app at all, as pointed out by Appleosophy. It can’t be enabled via Mission Control and there’s no sign of it in the operating system, marking its official demise.