dependencies {
  def nav_version = "2.3.5"

  implementation "androidx.navigation:navigation-fragment:$nav_version"
  implementation "androidx.navigation:navigation-ui:$nav_version"

  .......
}

buildscript {
    ext {
        kotlin_version = "1.4.30"
        nav_version= "2.3.3"
    }
// other code 
}