Find() doesn't support named arguments, so you're going to need to ditch the X = whatever part and just pass in numbers. But if you're just going to search the whole list(the default) you can just do Techniques.Find(skill name here). Unless you're worried about where in a list a technique is, just use the 'in' operator instead. It's more efficient, but it has a lower operator precedence than most operators, so be sure to always surround your_item in your_list in parentheses to head off any sneaky logic errors.

length(Techniques) and Techniques.len both give the length of Techniques. length() is safer to use as whatever list you're checking doesn't have to be initialized to anything to get a length. Techniques.len would give you an error if Techniques were null, but using length(Techniques) would not.