I see, so all these values are being entered by the user then? I don’t think you can dynamically add key-value pairs to a Object type custom property so someone correct me if I am wrong. I also don’t know how else you would keep a consistent json object.
Personally, I would probably probably insert each parameter-value into a dataset formed like the following
paramter value paramtervalue
paramter1 value1 paramter1:value
Then to display ALL paramter/value pairs, you would just need to do
groupConcat(dataset, paramterValue, ",") to display them all in a text field.
You would have to then convert the dataset to json for whatever you need later on. But having a dataset -> json conversion function is probably a good idea in general.