I have fallen down this Rabbit Hole of some people creating these incredible amazing beautiful sword-swinging animations. I tried looking for tutorials on Dev-forums, Youtube, etc. I have even tried contacting them but I can not find a clue on how these are made. They are not made with Trail effects or any in-game particles, these are animated using blender and meshes. If anybody knows how to re-create these, please get in touch with me by replying to this post.
I think these are Particles, these are probably custom made though.
Honestly, this looks like roblox particles + roblox personalized animations + particles. Thats the simple way to make it, but it would mainly depend on how smooth you do it.
In some cases you could even mix some particles to create something better, so I’d say thats sort of it.
Sorry for the 5 month old bump, but I can help you.
Dm me and I can tell you the secret.