Kibana Alert Action Message with Range Vaues

I am trying to output search timestamp range in alert notification message rather than the monitor start/end time. Using a 5 minute offset in search.

                  "range": {
                        "@timestamp": {
                            "from": "{{period_end}}||-6m",
                            "to": "{{period_end}}||-5m",
                            "include_lower": true,
                            "include_upper": true,
                            "format": "epoch_millis",
                            "boost": 1
                        }

UI indicates that only ctx variables are available for painless scripting. {{ctx.periodStart}} and {{ctx.periodEnd}} represent the monitor interval time. Any ideas on how to solve this?

Working extraction query code:
    {
        "size": 0,
        "query": {
            "bool": {
                "must": [
                    {
                        "query_string": {
                            "query": "\"Cause = 504 Gateway Time-out\"",
                            "fields": [],
                            "type": "best_fields",
                            "default_operator": "or",
                            "max_determinized_states": 10000,
                            "enable_position_increments": true,
                            "fuzziness": "AUTO",
                            "fuzzy_prefix_length": 0,
                            "fuzzy_max_expansions": 50,
                            "phrase_slop": 0,
                            "analyze_wildcard": true,
                            "escape": false,
                            "auto_generate_synonyms_phrase_query": true,
                            "fuzzy_transpositions": true,
                            "boost": 1
                        }
                    },
                    {
                        "match_phrase": {
                            "@owner": {
                                "query": "Production",
                                "slop": 0,
                                "zero_terms_query": "NONE",
                                "boost": 1
                            }
                        }
                    },
                    {
                        "range": {
                            "@timestamp": {
                                "from": "{{period_end}}||-6m",
                                "to": "{{period_end}}||-5m",
                                "include_lower": true,
                                "include_upper": true,
                                "format": "epoch_millis",
                                "boost": 1
                            }
                        }
                    }
                ],
                "adjust_pure_negative": true,
                "boost": 1
            }
        },
        "version": true
    }

I don't think this is possible for now. The fields accessible are pretty limited.