Hey, you could use RegEx for this, with the following expression: ^[A-Z] or ^[a-zA-Z].

So within the Tester, your 'Operator' is Contains Regex and your 'Right Value' is either ^[A-Z] (to find features that begin with any capital letter within the alphabet) or ^[a-zA-Z] (to find features that begin with any letter of the alphabet, may it be lower case letters or capital letters).

Thank you sooooo very much! Worked like a charm.