Reply To: Shift key will center the knife cut on both sides, is there way to center it only one side?

Actually, midpoint snapping centres all unconfirmed points (green). So when starting a new cut the first and second point are centred on their respective edge.

I suggest starting with a cut on the side face and then hold SHIFT when making the second cut. If needed you can always delete the first cut.

Or you can use midpoint snapping as you have, and then edge slide the vertex you don’t want at the midpoint.
You could also loop cut and edge slide a vertex or two.

Creating Ngons or triangles is not always ideal, but it will depend on the model and it’s use.
The ideal solution is based on thinking ahead, and how it may affect things later.