I think the basic problem is that the "Mutileader Label 18" object does not have custom parameters to begin with.
Can you select the "Mutileader Label 18" object, go to its settings Dialog and set the values of those parameters there? I can't because it doesn't have such parameters.
When you define what field to list in the schedule, that "General" group lists parameters GDL Objects usually have. But not all of them have all. In this case, "Mutileader Label 18" object does not have custom parameters.
I think this is why their value gets lost because they don't have the parameters to store the values in.
I hope this makes sense.
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