One clarification:
"in" has two behaviors:
- String search: Is a certain text inside a certain other text string?
- Membership: Is a given record inside a table of records?
Membership is not delegable today, but the string search is delegable with SQL.
So something like this would be delegable with SQL:
Filter(dbo.table,"find_me" in column_name)
This would attempt to return records where the string 'find_me' is in the given column of type NVARCHAR (text).
Filter(dbo.table, column1 in collection.column2)
This one means, "Filter the table where the content in column1 of the table is an entry in column2 of the collection." You'll receive some results, but it would not be delegable.
Let me know if this made sense.