=== Feature requested:
When I edit on a horizontal screen, I want to view my output next to my syntax, so I can easily check for typos and formatting.
=== Functionality/software changes
[] functionality goes into Wikieditor extension of 2010 text editor
[] add down arrow (chevron) and add an event handler to show or hide preview vertically stacked
[] add right arrow (chevron) and add an event handler to show or hide preview horizontally stacked
[] add breakpoints for vertical screen split editor
=== User interface changes
==== Screenshots/mockups:
{F34688250}
{F34688261}
{F34688262}
==== Interface text/changes:
A new icon will allow to expand and collapse the layout and switch between vertical and horizontal stacking.
https://www.figma.com/file/Jb6SALEoHWQRawSxscd3Ap/Wikipedia%2FLive-Preview?node-id=0%3A1
=== Does this need QA?
Yes