The list (1) works from custom menu, (2) contains values from your sheet, or any values, (3) supports single or multiple selections, (4) supports search by letters, (5) returns selected values to the script when the "Submit" button is clicked.
The list (1) works from custom menu, (2) contains values from your sheet, or any values, (3) supports single or multiple selections, (4) supports search by letters, (5) returns selected values to the script when the "Submit" button is clicked.