Styjun

Its Shift + Alt + 2 to split into 2 screens. More options are found under the menu item View -> Layout.

Once the screen is split, you can open files using the shortcuts:

1. Ctrl + P (From existing directories within sublime) or

2. Ctrl + O(Browse directory)

Inside sublime editor,Find the Tab named View,

View --> Layout --> "select your need"

Here is a simple plugin to "open / close a splitter" into the current file, as found in other editors:

import sublime_plugin

class SplitPaneCommand(sublime_plugin.WindowCommand):
 def run(self):
 w = self.window
 if w.num_groups() == 1:
 w.run_command('set_layout', 
 'cols': [0.0, 1.0],
 'rows': [0.0, 0.33, 1.0],
 'cells': [[0, 0, 1, 1], [0, 1, 1, 2]]
 )
 w.focus_group(0)
 w.run_command('clone_file')
 w.run_command('move_to_group', 'group': 1)
 w.focus_group(1)
 else:
 w.focus_group(1)
 w.run_command('close')
 w.run_command('set_layout', 
 'cols': [0.0, 1.0],
 'rows': [0.0, 1.0],
 'cells': [[0, 0, 1, 1]]
 )

Save it as Packages/User/split_pane.py and bind it to some hotkey:

"keys": ["f6"], "command": "split_pane",

If you want to change to vertical split change with following

 "cols": [0.0, 0.46, 1.0],
 "rows": [0.0, 1.0],
 "cells": [[0, 0, 1, 1], [1, 0, 2, 1]]

I regularly work on the same file in 2 different positions. I solved this in Sublime Text 3 using origami and chain with some additional config.

My workflow is ctrl-k 2 splits the view of the file in two (horizontal) panes with the lower one active. Use ctrl-k o to toggle between the panes. When done ensure the lower pane is the active and press ctrl-f4 to close the duplicated view and the pane.

In sublime global settings (not origami settings!) add

"origami_auto_close_empty_panes": true,

Add the following shortcuts

 "keys": ["ctrl+k", "2"], 
 "command": "chain", 
 "args": 
 "commands": [
 ["create_pane", "direction": "down"],
 ["clone_file_to_pane", "direction": "down"],
 ],
 
 ,

 "keys": ["ctrl+k", "o"], "command": "focus_neighboring_group" ,

I would suggest you to use Origami. Its a great plugin for splitting the screen. For better information on keyboard short cuts install it and after restarting Sublime text open Preferences->Package Settings -> Origami -> Key Bindings - Default

For specific to your question I would suggest you to see the short cuts related to cloning of files in the above mentioned file.

It is possible to edit same file in Split mode.
It is best explained in following youtube video.

https://www.youtube.com/watch?v=q2cMEeE1aOk

View -> Layout -> Choose one option or use shortcut

Layout Shortcut

Single Alt + Shift + 1
Columns: 2 Alt + Shift + 2
Columns: 3 Alt + Shift + 3
Columns: 4 Alt + Shift + 4
Rows: 2 Alt + Shift + 8
Rows: 3 Alt + Shift + 9
Grid: 4 Alt + Shift + 5

Kinda little late but I tried to extend @Tobia's answer to set the layout "horizontal" or "vertical" driven by the command argument e.g.

"keys": ["f6"], "command": "split_pane", "args": "split_type": "vertical" 

Plugin code:

import sublime_plugin


class SplitPaneCommand(sublime_plugin.WindowCommand):
 def run(self, split_type):
 w = self.window
 if w.num_groups() == 1:
 if (split_type == "horizontal"):
 w.run_command('set_layout', 
 'cols': [0.0, 1.0],
 'rows': [0.0, 0.33, 1.0],
 'cells': [[0, 0, 1, 1], [0, 1, 1, 2]]
 )
 elif (split_type == "vertical"):
 w.run_command('set_layout', 
 "cols": [0.0, 0.46, 1.0],
 "rows": [0.0, 1.0],
 "cells": [[0, 0, 1, 1], [1, 0, 2, 1]]
 )

 w.focus_group(0)
 w.run_command('clone_file')
 w.run_command('move_to_group', 'group': 1)
 w.focus_group(1)
 else:
 w.focus_group(1)
 w.run_command('close')
 w.run_command('set_layout', 
 'cols': [0.0, 1.0],
 'rows': [0.0, 1.0],
 'cells': [[0, 0, 1, 1]]
 )