Adding map to JSON

[csongorkeller]

Hi there,
how can I add a map to JSON object?
I've tried to plug it into ADD FIELD TO JSON OBject but doesn't work.
Also, a question if adding a field to JSON would work runtime after packaging the project, since it shows this message:

The node ' Add Field to JSON Object ' is from an Editor Only module, but is placed in a runtime blueprint! K2 Nodes should only be defined in a Developer or UncookedOnly module.