Which function replaces a specified string in the original string with a new string?

The function that replaces a specified string in the original string with a new string is indeed the Replace function. This function allows users to search for a particular substring within a string and replace every occurrence of that substring with a new specified string. This is particularly useful in data transformation processes where you may need to standardize or update strings within a dataset.

In contrast, the other options do not serve the same purpose. The Qualify function is used in Qlik Sense for handling field names to avoid naming conflicts and ensure unique field identifiers, rather than for string replacement. The TextBetween function retrieves a substring from a string based on specified delimiter positions, which is useful for extracting parts of strings but does not alter the original string. Lastly, the Left function is designed to return a specified number of characters from the start of a string, providing slicing functionality rather than performing replacement.

Understanding how the Replace function operates and its application can greatly aid in effectively managing string data within your Qlik Sense applications.