Hello,
I am working with alteryx for a couple days now and I am still quite impressed but also at the beginning of my journey. 
What I am looking for a the moment is a solution which I couldnt solve with exiting disussions for the first time (I believe I wasnt asking the right question).
Anyway, I do have a list where in one row IDs are listed. Some of them are double entries which I like to mark (e.g. "X" in a new column) or as an alternativ using the filter tool to separate them. I am just not quite sure which expression I do have to use. I guess I do have to use the [Row] expression but dont know how.
Can anybody help me here or guide me to the right discussion?
Thanks for reading it. 
Br