How do you call a non-schema field from a database that was cereated from a setfieldvalue function?
An error. 
But seriously, do you mean the fields in square brackets which get added to the schema because the field key did not exist?
Yes 
. What happened is that I have a string that changes it’s text value as per my code. Then on a button click, I will extract that text string and set as a new field in my DB. That means, I am not constrained with what is present on my DB but can be flexible as to what to be generated in the text. Is it possible to call those fields with square brackets? Or do I really need to set its field type after submission to DB?