I have a list of names and different key numbers. Column C is filled with names and the following columns F:X represent all the keys. In each row, there's an 'X' under the key number that person has.
On another tab, I'm listing some of these names using the formula FILTER. In the following column I'd like to list every key where there's an 'X' for that person.
For example, in Cell D3, I have this formula: =FILTER(Table1[Name, first name];Table1[UPDATE]="Add";""), which gives Peter. In Cell G3, I want all the keys that Peter has an 'X', so that in Cell G3, I will get: "1, 8, 15".
See File as attachment.

Test.xlsx