Create a list of the unique identifier for each duplicate value in Google Sheets

Question

In my Google Sheet I have got the Unique values and a count of the duplicates but I want to create a column that has the unique ID (UID) for each of duplicate values so I can decide on further analysis.

Using =VLOOKUP(D2,A$2:B,2,FALSE) I can get the first one, but how to I get the others?

A test sheet is in https://docs.google.com/spreadsheets/d/1WnGEsuuJcKsHVhpyYCX5EpmIxuKQEst5XVXgeETzxJ4/edit?usp=sharing

For

I'd like to see the UID column for PR120973-2^388.674 to be {1,6,20,25}

Answer 1

You can use FILTER/TEXTJOIN:

=TEXTJOIN(",",1,FILTER(B:B,A:A=D2))