Replacing duplicate list elements with a blank space but leave blanks and and maintain element count..?

Explode the list, use a duplicate filter to set the value of anything coming out of the duplicate port to blank then rebuild the list?

Edit: just noticed you need the first element to be replaced with a blank rather than the second which makes it a bit more complicated

Not necessarily. I think at this point, I would just settle for no duplicates/right number of elements.

Am trying your suggestion - ListExploder, DuplicateFilter, using AttributeManager on the duplicate port to set value to ' ' and plugging it all into ListConcatenator. Currently, though, LC cannot see any list attributes...

After exploding you no longer have a list, you need to rebuild the list before concatenating

If i could replace 8 transformers with one python caller though I'd probably go down that route

import fme
import fmeobjects

def replace_duplicates_with_blanks(feature):
    text = feature.getAttribute('text')
    list = text.split("|")
    list.reverse()
    newlist=[]
    for i, val in enumerate(list):
        if val in newlist:
            newlist.append("")
        else:
            newlist.append(val)
    newlist.reverse()
    separator = '|'
    newtext = separator.join(newlist)
    feature.setAttribute('newtext',newtext)