Hold some keys down and click the "Save Keys" button...

This page has triggers for CTRL-G and M-S-N.
String:

Key Code:

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When a key is pressed, it's added to an array.
When a key is release, it's removed from the array.
The array is written out to the text field each time a change happens.

Note that once your keyboard repeat comes on keys can no longer be added to the array.
This limits the maximum array size based on your keyboard settings.