Dashboard information

Some of the functions of Dashboard Widgets are available in Notification Center if you click on "Edit".

Purportedly, the old Dashboard stickies notes that are stashed in a ~/Library/Preferences/ .plist, are detected by the Catalina upgrade installer, and migrated to individual stickies folders in the new Stickies application. I have not upgraded my Mojave machine to Catalina yet to confirm that this indeed, does occur.

You can't. Dashboard has disappeared on Catalina

While it's true that Dashboard is gone many of the widgets live on as separate applications. Data in Stickies is moved to Notes as an example.