There are tons of settings posted on Github, and I just modified someone else's to get:
{"description":"Change right_shift alone to delete_forward", "manipulators":[{ "from":{"key_code":"right_shift","modifiers":{"optional":["any"]}}, "to":[{"key_code":"right_shift"}], "to_if_alone":[{"key_code":"delete_forward"}], "type":"basic"}]}
There are tons of settings posted on Github, and I just modified someone else's to get:
[1] https://github.com/tekezo/Karabiner-Elements