Adding/replacing apps in the app dock on Marshmallow

[steveljAC]

How do I add a app to the app dock on Android Marshmallow? Removing an app was easy. I tried the long press and moving the app to the dock region, but it pops back up above the dock. This is for a Nexus 5X.

 

[steveljAC]

Actually, the long press and move does work. Except on what I created using Notifier app, which is actually a widget. Ooops