Every one love sublime in these days. Sublime Text supports multiple view panes. Panes split the window into vertical and horizontal views that contain document tabs. Each pane can contain multiple tabs. The views are independent but joined together. They are two (or more) views on the same text buffer and all views are updated as one pane is modified (it is not necessary to save the document to update the other views).
View > Layout > 2 Columns
File > Clone File