If you open this template with Godot 4.2, there is the option to upgrade it and you should be fine.
The shooting mechanic can be modified to your needs. Actually, it's really easy to spawn 3 bullets at the same time.
You can change the logic of the wall slide so the player is "glued" to the wall until you press the jump key.
The key feature of this template is that you have a finite state machine that can handle different animations and states, is ready to use or to modify to your needs and is very simple to understand. The possibilities are endless !