Thank you for that ! After having tried and tested the 6's swordfish, I can finally find the logic in the method you proposed to finishing the puzzle !
I did not know that such a combination of swordfish could exist, I had previously understood that 2 or 3 digit possibilities in a single row/column must have EACH a corresponding possibility in column/row, before a swordfish could exist and only then eliminate all other possibilities of those rows and columns.
In this case, I thought that r1c4 must have been a part of the swordfish for their to be a swordfish in the first place ! -- which is why I could not see a visible swordfish - but now I know differently !!