How to update the data table column value by identifying a specific with the condition

have a look here:
[HowTo] Overview on different options for grouping data and processing the groups - News / Tutorials - UiPath Community Forum

later it will discuss the updatings on a subset of rows

we have the options:

  • LINQ Where filtering and returning the result as a collection (list/array of DataRows)
  • DefaultView approach as described

As long we do not use Statements/Activities that are changing the DataTable identity - DataRow link we can filter and update directly on the Master