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I was looking for this feature as well and I discovered that you can already do it with:

{ "keys": ["ctrl+up"], "command": "move", "args": {"by": "stops", "empty_line": true, "forward": false} },

The documentation for the move command is here though it doesn't explain what the by:stops option does. My investigations found that the by:stops instruction uses the empty_line, word_begin, word_end, sub_word_begin, sub_word_end, punct_begin and punct_end boolean options to determine which points to stop at.