The Blend Space 2D is the base component of WBP_FloatSpace2D and behaves like a 2D slider. You can move around the white dot by clicking and dragging. OnValueChanged will give you a vector from (0.0|0.0) to (1.0|1.0) depending on the location of the dot. (0.0|0.0) is upper left, (1.0|1.0) is lower right.