Layered blend animation will not be applied inside the animation sequence, instead, you will need to set it inside the animation blueprint. So that you can see the result during the gameplay.
From this statement of yours, you should have said you don’t know instead of proposing the idea to avoid doing this method.
Base pose should be set to your lower body animations and blend pose should be set to your upper body animation. Pay attention to the right side window, how I set the layer setup based on the bone name that you want to create the separation from.