KQL search problem

Thank you very much for your help, but it still does not work.

Summary:

The message field contains a long string, including "delimiters" like | , key-value pairs like cod=491234567 etc.

In the index patterns, we see that the field is of type string not text. Or is that the same? (It is marked as searchable.)

I need to find records/entries whose message field contains cod=49 as a substring.
What query do I need to use for this?

These are the things I tried, with variable results, but never what I wanted:
Query: message:cod=49
Result: Finds entries with substring 49 OR cod, but not (only) cod=49

Query: message:"cod=49"
Result: No results match your search criteria

Query: message:"cod\=49"
Result: No results match your search criteria

Query: message:cod\=49
Result: Expected AND, OR, end of input, whitespace but "" found. message:cod=49 ---------------^

Query: message:"*cod=49*"
Result: No results match your search criteria

Query: message:*cod=49*
Result: No results match your search criteria

Query: message:"*cod\=49*"
Result: No results match your search criteria

Query: message:*cod\=49*
Result: Expected AND, OR, end of input, whitespace but "" found. message:cod=49 ----------------^

It worked differently in the previous version of KIBANA (Version: 6.2.4.)
There I query withmessage:*cod=49* and the result was all logs that contained xxxx, cod=49xxxx, as a substring in the message field.