I have used superglue for years in and out of the tank.... It does not kill the plants or the fish unless you stick a fishie to your plant then that can be hairy.
Superglue has also been used by reef keepers to hold down live corals for years.
Once superglue comes in contact with water it skins over right away so what I do is put a drop on what I want to attach to like a wet piece of wood or rock let it skim them press the plant into the glue breaking the film that reforms right away holding the plant down.
I have used it to hold gown all types of mosses, ferns, and other stuff in my tanks. Only drawback I have found is if there is an area you can see the glue it will be white until the moss grows to cover it or it ages for a coulple of months.
Super glue is easier and a lot more versitle than string or mesh you can stick stuff to things you never could before and get them to stay.
I have 8 tanks all with superglued plants and rocks in the tanks some are over a year old and some are a few weeks in age no deaths of plants are animals in any. Some were fully stocked some just plants when the superglue was used.
Best type to use is the gel gives you more control by the way.
You can just search super glue on this forum and find plenty of post that say the same thing as I just posted.