Currently, arrows of best moves found by Stockfish are shown in varying sizes. The arrow of the best move is colored blue and the other best moves are partly transparent. An example for this is shown below. Note that three multiple best lines by Black are being shown in the side (Qxe4+, Be6, a6) and that there are arrows depicting the first moves of these lines.

Currently, when threats are being shown, only the best threat by White is depicted with arrows. An example is shown below. Note that the only arrows depict 10... Qxe4+ (Black's best move) and 10. f3 (White's best move/threat), despite that there are three multiple threat lines by White shown in the side (f3, Bd3, Be3).

I think that the multiple threat lines by White (f3, Bd3, Be3) should be depicted with arrows in a way similar to how the multiple best lines by Black (Qxe4+, Be6, a6) are shown.