Currently the process of creating new Anim Layers in UE5.1 is broken. Its fixed in the main UE5 branch and I’ll give you a quick outline on how to get that for yourself.
disclaimer - This will only work if you have github access to the engine. Anyone can request this on the unreal engine homepage
You unfortunately do need a source build of the engine to implement this fix. The 2 issues with the linked anim layers in 5.1 is that you can’t add implemented interfaces to animation blueprints and you can’t drag the generic anim layer node onto the the graph. These 2 bugs will completely stop you from adding any new anim layers to your blueprint
To fix this bug, implement these 2 fixes, luckily for us the bug is contained to a single file