Use clamps to reduce the scale value.
Add movement Inputs “Scale” is a multiplier. By Default the scale is -1, 0, or 1.
1 * Max Walk Speed = Movement Speed
The image below reduces the Scale by half.
0.5 * Max Walk Speed = Movement Speed
Create a Function that you pass Axis X and Y to, then determine your movement direction and adjust the scale as needed, then pass that value to Add Movement Input.