Note that array functions can only be used in rollup fields, or when the input field is a linked record or lookup.

The docs note array functions only work with specific field types.

The square bracket examples are also misleading - if you plug ARRAYUNIQUE([1,2,3,3,1]) into a formula field, for example, it will also error out. The numerical values need to be replaced by valid field types, and the square brackets removed entirely. For example, this would run properly in a formula field ARRAYUNIQUE({some linked record field}, {some linked record field}).

I understand it’s a misuse of the formula and not a synthaxe error.

Thank you

If you want to join the fields together into a single string, you can use the & operator:

{Field 205} & ";" 

& {Field 206}  & ";"  

& {Field 3}  & ";" 

& {Field 4}  & ";" 

& {Field 207}  & ";" 

& {Field 6}

{Field 205} & ";" 

& {Field 206}  & ";"  

& {Field 3}  & ";" 

& {Field 4}  & ";" 

& {Field 207}  & ";" 

& {Field 6}

Thank you Kuovonne,

It worked out but I had to switch you ; by a single space to have the new field recognized as a multiple select field.

Glad you found a solution. I used a ; in my formula because you had one in your original formula. You didn’t say that you were then going to convert the formula field into a multiple select field.