JSON New Form

Sobiepan Unfortunately, No. You cannot check if current list form is new item form or edit item form using JSON formatting.

Check my answer on this thread for detailed information: How to detect Edit vs New when styling custom list forms with JSON? 

You have to customize list form using Power Apps to show/hide fields based on form mode (new/edit): Displaying fields when creating new item and them hide them when editing the item, and viceversa. How to do this? 

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