"Show Cursor Info" is available when accessing the Tool menu item in Widgets mode. Is there any way I can use this data when developing some kind of app in Decker?
Yes!
In your code you can access the pointer interface, which lets you get details about the position and state of the mouse cursor. There's details in the Decker Reference Manual. https://beyondloom.com/decker/decker.html#pointerinterface