Best way to handle navigation - help please!

I have a Storyline 360 file that needs to show three navigation buttons on each slide, as follows: Restart, Back and Next.

The Restart button will go to different places at different points in the story - usually the start of the scene, but not always.

The Back button will go to the previous slide OR the previous layer, depending on the content of the slide.

The Next button starts every slide as hidden and becomes available at different times, according to the content of the slide. It will go to either the next slide, next scene or a specific layer.

I'm currently handling these manually as I can't see how I could put them on a Slide Master because of the different needs of each button.

Does anyone know of a better way to do this?

I'd be very grateful for any help!

Thanks in advance