I am trying to make a slice using CONTAINS. The column I am trying to use is a Ref column, so the actual text is not in the sheet, but the ID of the parent sheet. How do you use CONTAIN with a Ref column of the child sheet?
I suspect that you actually will want to use the IN() function.
CONTAINS() is meant to operate on strings or text values to determine if one string is “contained” within another string. See article below for examples.
IN() operates on LISTs to determine if an item is one of the LIST items. Article below.