Is there a way to configure the user filter in record for the field for which we are not storing the data in db
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Yes, you can create a custom record field and then create a user filter for that field.
docs.appian.com/.../custom-record-fields.html
I'm just capturing the value in interface by using expression rule based on null values. I'm not storing it anywhere
Do you mind explaining your use case in more detail? Data that is not stored anywhere cannot be used.