Here is the Sublime Text 3 solution to display files in adjacent group panes so that you can you work on multiple files simultaneously with the files in view.
Sublime Text Group Panes
Open a file in your editor and then create a second group pane with the menu items
View > Groups > New Group.
This gives you a vertical divider with a new file group pane on the right side. Click in the right pane and then open another file. The files are displayed adjacent to each other like this:
Make Additional Groups
Open another file in either of the groups and (with the file selected) use the menu items
View > Groups > Move File to New Group. This will place a horizontal divider below your right side pane with the new file in the bottom right corner.