chatgpt cannot help me! (return value from another row that has another variable in common)

1. Split off an un-loaded copy of the table
2. Filter to 20/21
3. Drop all but lemonway_id and user_id
4. Remove duplicates table-wide
5. Group-by lemonway_id with an "average" on user_id, and a row count
6. Change the "average" code to Text.Combine to get a concatenated list of users in that cell.
7. Filter out row count 1 (the ones where there is no repeat)
8. Merge this table back into a copy of your original matching on lemonway_id and expanding out your concatenated list of users.

Conversely in power bi you can use the original table to supply a matrix with lemonway_id and user_id as rows.