This does not exist in a reliable fashion for the general case if you want something from the real world.
In the real world, truly non-lethal weaponry does not exist. Rubber bullets have killed people, pepper spray has caused reactions which have killed people, tasers have caused cardiac arrest. Weapons that are meant to incapacitate are generally referred to as "less-lethal" because something that is reliably "non-lethal" does not exist.
But you can come close when you know a lot about your target
Zoos for instance can sedate large predators at a distance relatively reliably, but for that they have to know their target's approximate weight and health history. They then use a dart gun that delivers the proper dose. Even then it can take a substantial amount of time to properly sedate the target.
Also, this is not applied to the blade but used in a syringe-like dart.
There are poisons that are applied to a blade, or more often an arrow, successfully in the real world, but they are precisely that, a poison which has a solid chance of killing the target. They do not reliably knock someone out or paralyze them temporarily.
This is an incredibly common trope in fiction so for world-building purposes you don't need much
Most people over-estimate how easy this would be in the real world so if you are doing this for fiction virtually all readers will accept it if you hand-wave it.
If you want to acknowledge how hard it is but do it anyway in a sci-fi setting you can have nano-machines control the dosage and thus become reliable through precise application of advanced tech. In a fantasy setting, your poison can be magical. In a realistic pre-modern or even modern setting, you are probably down to either handwaving or saying your character is just that good and so was able to calculate the dose and deliver it accurately.