How to Return Text from Column 1 if Text in Other Rows Match

56008769 

you can use the filter formula

Hello 56008769,
Use this array formula on B17

=IFERROR(INDEX($A$2:$A$13,SMALL(IF(B$2:B$13="X",ROW($A$2:$A$13)-ROW($A$2)+1),ROW(1:1))),"")

56008769 

As variant,

=LET(day,B2,tasks,BYROW(B3:B14,LAMBDA(r,IF(r="X",OFFSET(r,0,COLUMN($A$3)-COLUMN(B2),1,1),""))),FILTER(VSTACK(day,tasks),VSTACK(day,tasks)<>""))

You can drag the formula to the right to complete all days of the week. If the number of tasks may increase you can just set the ranges to row 100 or whatever in order to make sure all tasks are covered. If you are on Excel 365, this will automatically get your tasks updated if any changes.

See attached document.

56008769 

Practically same as above, but in one spill

=LET(
  marks, $B$3:$H$14,
  tasks, $A$3:$A$14,
  header, $B$2:$H$2,
  seq, SEQUENCE( COLUMNS( header ) ),
  filtered, BYCOL(marks, LAMBDA(v, LAMBDA( FILTER(tasks, v <> "" ) ) ) ),
  combined, IFNA( DROP( REDUCE("", seq, LAMBDA(a,v, HSTACK(a, INDEX(filtered,1,v)() ))),,1), "" ),
  result, VSTACK( header, combined),
  result
)

56008769 Just for fun, here's another approach for MS365 using some array reshaping functions:

=LET(
    table, A1:H13,
    vals, DROP(table, 1, 1),
    test, vals <> "",
    n, ROWS(vals),
    v, SORTBY(
        TOCOL(IF(test, TAKE(DROP(table, 1),, 1), "")),
        TOCOL(IF({1}, SEQUENCE(, COLUMNS(vals)), vals)),,
        TOCOL(IF(test, SEQUENCE(n))),
    ),
    VSTACK(
        DROP(TAKE(table, 1),, 1),
        TAKE(WRAPCOLS(v, n), MAX(MMULT(EXPAND(1,, n, 1), N(test)), 1))
    )
)

Adjust the table range reference as needed.

Sample Results

56008769 

With some reduction:

=DROP(
    REDUCE(
        "",
        DayOfWeek,
        LAMBDA(acc, v,
            LET(
                vector, XLOOKUP(v, DayOfWeek, tally, ""),
                r, SUM(N(vector = "x")),
                sorted, SORTBY(tasks, vector, 1),
                actual, TAKE(sorted, r),
                IFNA(HSTACK(acc, actual), "")
            )
        )
    ),
    ,
    1
)