Enum data from other column error

[simone_checchin]

Hi to all,
I have this problem.
I’m trying to populate an Enum column with another column data and also allow other values but when i try to put the formula in the seggested values it shows me this message
“The expression is valid but its result type ‘List’ is not one of the expected types: Enum”
I’ve tryed this formula UNIQUE(table name[column name]).

Many thanks.