It sounds like CarouselView might not be released for a long while. See: https:\\forums.xamarin.com\discussion\144717\what-is-the-direction-of-using-a-carousel-in-xamarin-forms.
Are there any plans for CarouselPage to support ToolbarItems?
Not tested obviously but in Forms 3.3/3.4 you can override the page title with your own view, tested this concept with modal pages and master detail pages. I have no idea is it works with Carouselpage, it's not part of the supported API so I haven't investigated.
CarouselPage does seem to support NavigationPage.TitleView. It does not even seem to support Title.
Use content page with supported carousel view plugin
For example https://github.com/AndreiMisiukevich/CardView
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