You did not elaborate on the reasons to change a field (Competitor Flag) in the load script? in general we load data from legacy systems without transforming it, because Qlik's models represent a view of the sourced data, your request breaks that rule. If we know more about the reasons to do that we could be able to share some ideas with you.
Arnaldo Sandoval A journey of a thousand miles begins with a single step.
The reason behind is that the original data from legacy system are wrong for some reasons. In this case, there is about a dozen of products with wrong competitor flag. I have built a few sheets based on it so there are various line ,pie , table charts and panel filters attached and relevant associate other fields are linked. Rather than changing expressions one by one for each fields at each sheet for each chart, I am seeking if we have a good solution to edit data at loading script.
Since we have where statement which is able to do some filter work at loading script, wondering if we have similar logic way to solve this problem too.
Now, I understand your issue, perhaps the best approach if for the business to fix the data at its source; if this is not possible, then I suggest you to introduce an Excel file with two columns; as the screenshot illustrate:
The in your Load Script, you implementing a mapping logic to this data, with something like this: