Create new record whilst inside subtable

Is it possible to create a record whilst you are already in a record of a subtable? The record in the image is from a subtable I would like to select the record and with the reversal, button add a new record instead of changing it, I can create a record but the relationship is not maintained.

let reversal := Amount;
let travelling_amount := Goals.'Travelling Amount';
let result := travelling_amount + reversal;

Goals.('Travelling Amount' := result);

let new_reversal := (create Milestones);
new_reversal.(Type := 2); //Reversal
new_reversal.(Amount := reversal);
new_reversal.(When := today());
new_reversal.(Submitted := true);
closeRecord()