Ok then, try with this one,
NOT "\"IMPORTANT\": {}," | rex mode=sed "s/...//g" | rex max_match=0 field=_raw "(?s)(?!\IMPORTANT\":\s{)\s{9,}\"(?.?)\":" | rex max_match=0 field=_raw "(?s)(?!\IMPORTANT\":\s{)\s{9,}.?(?::|:\s+)(?\d+)" | table timestamp KEYS VALUES
Let me know if it works.
EDIT: Improved. You have to scape quotation marks after the NOT operator, notice the doble quotes. This will filter events without "KEYS".
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