How do you split and unsplit a window/view in Eclipse IDE?

You can open a new editor from the Window menu.

This will give you your current editor once again.

If you right click on one of the tabs, one of the options should be New Editor (for me, it's at the bottom). Select that, and then drag the new tab onto the bottom scroll bar of the code editor, which will split the editor panel in two.

Just click and drag editor title to left, right, top or bottom

This is possible with the menu items Window>Editor>Toggle Split Editor.

Current shortcut for splitting is:

Azerty keyboard:

• Ctrl + _ for split horizontally, and
• Ctrl + { for split vertically.

Qwerty US keyboard:

• Ctrl + Shift + - (accessing _) for split horizontally, and
• Ctrl + Shift + [ (accessing {) for split vertically.

MacOS - Qwerty US keyboard:

• ⌘ + Shift + - (accessing _) for split horizontally, and
• ⌘ + Shift + [ (accessing {) for split vertically.

On any other keyboard if a required key is unavailable (like { on a german Qwertz keyboard), the following generic approach may work:

• Alt + ASCII code + Ctrl then release Alt

Example: ASCII for '{' = 123, so press 'Alt', '1', '2', '3', 'Ctrl' and release 'Alt', effectively typing '{' while 'Ctrl' is pressed, to split vertically.

Example of vertical split:

PS:

• The menu items Window>Editor>Toggle Split Editor were added with Eclipse Luna 4.4 M4, as mentioned by Lars Vogel in "Split editor implemented in Eclipse M4 Luna"
• The split editor is one of the oldest and most upvoted Eclipse bug! Bug 8009
• The split editor functionality has been developed in Bug 378298, and will be available as of Eclipse Luna M4. The Note & Newsworthy of Eclipse Luna M4 will contain the announcement.