How to add internal links / in app links
This functionality allows you to create links to a feature in your app from another feature.
From the feature places , custom page :
In CK editor (text editor) there is a new button :

To open the menu from source code , click on the insert in-app link button :

Once you have clicked this button , a new menu pops up :

Select the feature you want to link, press ok and it’s done !