Working with the Jam nodes. - GalanCM/Godot-Jamkit GitHub Wiki
Each of the nodes — JamTitleScreen, JamGameOver, and JamTutorial — are designed for use in two different ways: scene inheritance and direct modification.
For most needs, scene inheritance should probably be sufficient. This can be done by going to Scene > New Inherited Scene
in the menu, and selecting the node you wish to inherit. If you find that you need more control you can always load the scene directly or modify the script.
For the sake of simplicity, this guide will focus on the scene inheritance approach.