I think 'value list' is a good idea, you can set the processing method as 'build value list' and map to clipboard to a value list property as map to key. Also you have Field format as 'custom definition' right?
Create a Pare Delimited Rule with \n as a separator and in processing method select build value list. In Parsing details maptokey should be mapped to property of valuelist.
In the activity, loop through created value list property and call another Pare Delimited Rule comma as a separator. In Parsing details maptokey provide the pagelistproperties (like Address(1).city)