Knives sold in scuba shops for divers have a line cutter knotch, and trust me, when you're tangled in monofiliment line under water

it will not be slack. Sissors are an interesting idea but I don't think I could use them if I were wearing gloves and they would be hard to hold onto and operate with cold hands.
The best idea is to not have any monofiliment line or anything else laying in the kayak that you could could get tangled in. The knife is a backup in case you forget that advice.
I carried 2 knives when I was scuba diving on wrecks and there was always a lot of monofillinment line to get tangled in but the only time I needed a knife was to cut the wetsuite off of a girl who had drowned. Then I yelled for someone to give me a knife which Marianne did. Later I felt a little foolish when I realized I had one strapped to my leg and one to my arm. The girl was pronounced dead after we had done CPR for a couple of hours on the way to shore. Not the best day of my life.
But we're talking about kayaking not diving and if you get down to where there's a lot of monofiliment line you've got bigger problems than you can solve with a knife or sissors.
Dickc