By a trail for melee weapon, you mean a trail a melee weapon leaves behind that blocks/ harms enemies?
The shodos can get messed up when they're too small, so this might not work.
I might be able to modify the script for it to work but not in the near future.
You should try the asset store, I remember seeing a solution for line collisions there.
If that doesn't work remind me in a few weeks, I might be able to help out :)