In Forms, I suggest a toggle button to the left of the 4 current button.

When pressed, it shows the default values to be used for new items; when not pressed it shows the item current values (as it works now).
It should be possible to change any default values before creating the new item (as can now be done for the current item).

Also, to make sure that we know that we are looking at default vs current values, I suggest that the Field/Tag font is changed when the button is pressed e.g. to blue or italic or both.