When we set the action of “Set values in some column in this row”, we pick up the field name one by one and then assign the value either expression or textual value for configulation.
For the moment, even afer one certain field is selected, the same field can be selected continuously. Nobody will pick up the same column multiple time in this particular case, as it will raise an issue of conflict when app creators enter and assign different value for the same field.
Ideally, once the field is selected, then the same field should be removed from the dropdown list from the subsequent selection of the name of the field to avoid us to pick up the field which is already “picked up” and value is assigned for action.
Hope this makes sense.