you can use Column Expressions node. There you’ll find both case syntax and substr() function. Also you can use classic if/else which might be simpler for your case.
For your specific example (in both your questions) I would probably opt for the Rule Engine approach.
If you are still looking for an alternative, you can use the “almost undocumented” syntax of the String Manipulation node to achieve the desired result.
i.e. Assuming you have a table with “column1” containing your data, then the following in String Manipulation would also return the required result:
In this case it says that if the column matches the regex beginning 20, 11 or 22, then return “E” otherwise if it matches the regex beginning 23 or 24 return “L” otherwise return “NA”