I am offering a caution

regarding using string in the garden.
Cotton string may hold up in the sun okay for your trellising but it will not deteriorate in a compost pile quickly.
One of the worst advice that I ever gave was to a whole roomful of gardeners. I said that I used cotton string in the garden and just composted it with the plants at the end of the season. In the real world, I had just done this and didn't know the results. What a Mess!
After leaving it to compost for a
second year, it was still a Mess.
I
suspect hemp string would compost more quickly. I don't use hemp string because it can only remain intact for a couple of months, probably because of our intense Summer sun. However, I'm assuming nothing on composting string after the Mess that I made for several seasons.
Steve