Checking for duplicates is not too complicated. What is complicated is integrating this with the field editor so that you have the option to cancel if there is a duplicate, that is what has held up implementing this.
In the meantime, here is a simple 3 line program that will display an alert if the current field contains a value that is duplicated elsewhere in the database. You don’t have the option of cancelling and going back to the previous value, but it will alert.
if linecount(lookupall("",info("fieldname"),«»,info("fieldname"),cr()))>1
alertsheet "This is a duplicate value"
endif
You could use this in a standalone program, or you can put it in the code panel of a field so that it runs automatically when the field is edited. Doing that makes a feature that is similar to how Panorama 6 worked, but without the option to cancel and go back. You would have to manually re-edit the field.
I have tested this on text, numeric and date fields – it works on all types.