The repair button/function in the player's inventory or in workbenches does not interact with a Legendary Repair Kit.
Tempersmith T4 Blacksmith thralls can craft the Legendary Weapon Repair Kit at the Tinker's Bench. So don’t waste countless hours searching for them in this current build. Legendary Weapon Repair Kits restore the item to 100 durability.
Same goes for the named Alchemist Thralls that can make the White & Black Dyes.
And no, they don’t spawn in during purges. If anyone says they do they are giving false information if a person that says they do spawn simply ask them, “Where? Where did you specifically find it?” They will never have a clear answer – and “They roam, they aren’t in a static spawn location.” is an invalid response. BUT - These Thralls do NOT spawn on their own in the current build. The list of Thralls given in this video is accurate – they can craft the Legendary Repair Kits. “To those saying they have Maev the Magnificent or any of the other named Blacksmith Thralls but it can’t craft the Legendary Weapon Repair Kits - just because it’s a named Thrall does not mean it can craft Legendary Weapon Repair Kits.
Short summary all those thralls don’t spawn in this current build of the game. When i watched Just Horse’s youtube video on how to obtain legendary repair kits I noticed this comment pinned.