Add item in refenrence List by fomula?

[user12]

I want to append item in the reference List field by fomula. so I just append or concat
normaly do in python list.

but they show inappropriate sign even C is in the TEMP2.
first glance, I Think it is just because I just return list .A field not whole list
I return $A not $A.A but after that C is disappeared.

I don’t know how to solve it

[jperon]

You should use this formula:

$A.id + Temp2.lookupRecords(A='C').id

or this one:

_l = $A.id
_l.append(Temp2.lookupOne(A='C'))
_l

The problem with your formula was you weren’t working with record ids, but with values.

[user12]

Thanks! it solved!