The options below are common to both 1D and 2D blending.
You can alter the “natural” speed of the animation clips using the animation speed number fields (the columns with a clock icon at the top), so you could make the walk twice as fast by using a value of 2.0 as its speed. The button rescales the speeds of the clips so that they correspond with the chosen minimum and maximum values of the parameter but keep the same relative speeds they initially had.
Note that the drop-down is only available if all the motions are Animation Clips and not child Blend Trees.
You can mirror any humanoid Animation Clip in the motions list by enabling the mirror toggle at the far right. This feature enables you to use the same animation in its original form and in a mirrored version without needing twice the memory and space.