Sage 7 help horizontal lifter fail

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If I understand correctly, your question is about using horizontal scrollbars for code excerpts that are wider than the column width in SageMath documentation pages.

I'm not sure whether it depends on the browser or OS or their settings, but in my configuration what I observe is that horizontal scrollbars appear once the mouse pointer is on the scrollable part and I start scrolling.

How to scroll horizontally depends on the trackpad or mouse.

In my configuration however, with the mouse cursor on the scrollable part, scrolling even vertically makes the horizontal scrollbar appear, and then I can click into that scrollbar to scroll horizontally by click and drag.