Ok with 3 parallel tracks the layout would be a bit different. You would ideally make it so that it would be easy for trains to pass each other no matter which direction they’re travelling so that you always have a free track for a train to enter from either direction. Tracks on passing loops should always be signalled uni-directionally, so you would have two tracks that would be signalled in the same direction, and one track signalled in the other direction.
However, it’s worth bearing in mind here that passing loops should not need to be more than 2 tracks to allow trains to pass each other. If you’re approaching the need to add an additional line, then you need to think about doubling the entire line and allow block signalling to handle the additional capacity.