I am currently working on using json strings as input for my RAP generator tool.
Here I ran into the problem that I had to provide a (very) long json string as an input for a class that is run as a console application.
But also when using a simple json string such as this one (taken from
Wikipedia) it is not possible to use cut & paste to work with it in ADT.

Error when using cut and paste with default editor settings
... unless you know which settings you have to change for your ABAP editor in ADT.
From the menu choose
Window -->
Preferences and there
ABAP Development -->
Editors -->
Source Code Editors or you search for
source code editors in the
Preferences dialogue.
Here you have to activate the check box
Escape text when pasting into a string literal.

Preferences - Escape text when pasting into a string literal
When you now use cut and paste and paste a long string, a json string or even an xml string to your source code within the placeholders for a literal
json_string = ''.
all strings will be wrapped automatically

Result