Start by opening your Slideshow. If you want to change the names of the buttons, you have to switch from the Slideshow Editor to the Statistic Editor.

Click here to Switch to the Statistic Editor.

Select "Statistic".

Click into the title of the top of the visualisation and type in the name you want for its button.

At the left, select the next visualisation.

Repeat the steps for each visualisation.

When you're done, don't forget to save your changes.

You have successfully changed the names of the Slideshow buttons.