Listing value of Subtable in a Text Field

Support
1

I have a subtable in my sheet, lets give for example A1 and A2

Then I created a free text field with the formula “A1”
I want to list out all the selection in this field, but it just shows all the selections in one single string. Can I add a comma to separate each selection in this field?

2

the closest build-in function is UNIQUE(A1,“,”)
But it only show “unique” values.