Hello Iffaf,
Thanks for sharing your screenshot with me.
If you want to remove single slides from the menu, you can do that too!
Under player properties > menu, select the scene or slide title and click Delete heading (the trashcan icon) below the menu.
Take a look at the article below for additional information:
Storyline 360: Customizing the Menu
If you need additional assistance with this, I'd recommend opening a private support case with our talented Support Engineers. They'd be happy to look at your file and investigate further!
Hope this helps!