...
This field should be populated with the key of the value to be inserted. An example could be “JPEG:Compression Type = Baseline“, where “JPEG:Compression Type“ is the key, and “Baseline“ the value. Multiple keys, separated by , can be specified. In this case, the first key for which a value can be extracted is used. Thus, multiple keys can be used to provide fallbacks.
These key-value pairs are found using this tool
...