Horizontal Scroll Panels?

You could group the scrolling panel with a transparent shape and then rotate the group 90 degrees.

Thanks for the tip Michael.  It worked for this:

https://360.articulate.com/review/content/6af15e36-30e2-4ef4-8ba0-a9c5cea229fd/review

But sadly after grouped, was unable to edit the text or images, even when clicking on their layer in the timeline.  On screen the content is displayed in a jumbled up way.  See attached.

But for scenarios when the content is set in stone, this is an excellent solution.  

Thanks

It seems like an acceptable workaround. Hopefully, Storyline can let users decide on vertical or horizontal scroll in the future.