I added the following key in the DETextKeyBindingSet.plist file.

<key>My Custom Actions</key>
<dict>
 <key>Custom new down line</key>
 <string>moveToEndOfLine:, insertNewline:</string>
 <key>Custom new up line</key>
 <string>moveUp:, moveToEndOfLine:, insertNewline:</string>
</dict>

The custom new down line can be assigned with cmd + return for normal operation.
However, the custom new up line key, when assigned with the cmd + shift +return keys, will cause the
it will be treated as shift + return, which is the default key in xcode.

If you remove all duplicates of shift + return and cmd + shift + return keys and assign custom new up line as cmd + shift + return, the behavior is treated as down line -> end of line.

Also, if you assign the custom new top line with another key, such as cmd + j, it works fine.

How do I assign the custom new up line key as cmd + shift + return?

I tried to change DETextKeyBindingSet.plist
Changed xcode, but cmd + shift + return keys remain unchanged