Comprehensive and Detailed Explanation From Exact Extract:

The correct way to change the contents of a row in an internal table is by using the MODIFY statement.

MODIFY allows updating the existing entry in an internal table based on its key or position.

If the row exists, the statement replaces the data; if not, it inserts a new row depending on the internal table type and whether a key is specified.

INSERT adds new rows but does not modify.

APPEND adds entries at the end, and UPDATE is for database tables, not internal tables.

This behavior is consistent with the ABAP programming model used in both classical and RAP-based developments when manipulating internal collections or buffering data in memory during behavior pool execution.