This may have been asked by other users but I’ve not been able to find it. Is
there any way to disable the horizontal scroll bar so I don't keep
inadvertently expanding my page horizontally whilst still keeping the auto
addition of vertical space?
Disabling the horizontal scroll bar wouldn't do what you want anyway.
That would just make it so you couldn't scroll left or right even if you
needed to.
It is possible to set a specific page size so that you don't keep
expanding the page. However, the setting that most people seem to want -
a specific width with unlimited length - is not available.
Generally, the best advice I can give you is to just stop doing the
things that cause the "page width" to expand. Just don't write so far
over to the right. If you don't have enough room to write then use the
Full Page View button to give more room but then don't write all the way
up to the edge.
I'm sorry if it is not what you wanted to hear, but it is the best we
got.