cocoa app is not displaying in xcode 11

What do you mean

it's showing only App, how to install cocoa app in xcode

Which App ?

Which Cocoa App

What do you mean by installing an app in XCode ?

i want to create cocoa app project in xcode but it is not showing, and i don't know how to install cocoa package in xcode

Choose App. That's what Apple calls the Cocoa App project template now.

In File menu

Select New > Project…

Select MacOS tab

Select App in Application part.

Give a name to the project

Check if you want SwiftUI or Storyboard in User Interface field

Leave the other checkboxes unmarked.

Type Next and select the directory in which create the project

You're done.