You are right that the outputting of only Long from the Expression node is problematic The Long vs Int issue with the Expression node is further discussed in this thread based on the 5.3 release, and in the graphic I noted a number of nodes for which this would be an issue, including the Counting Loop…
In the Variable Expression node (I’m looking at KNIME5.4.4 but this functionality may have appeared in an earlier release), it is possible to specify the output type as either Integer (int) or Long (long int).