This is the backdash state from the common1.cns (Used by characters such as KFM that do not have their own common1, but instead refer to the common1 in the data folder). You can create your own state 105 within KFM's .cns file.
; Hop backwards
[Statedef 105]
type = A
physics = A
ctrl = 0
anim = 105
sprpriority = 1
[State 105, 1]
type = VelSet
trigger1 = Time = 0
x = const(velocity.run.back.x)
y = const(velocity.run.back.y)
[State 105, 2]
type = CtrlSet
trigger1 = Time = 2
value = 1
[State 105, 3]
type = ChangeState
trigger1 = Vel Y > 0
trigger1 = Pos Y >= 0
value = 106
The type and physics will need to be changed to S or C (Standing or crouching since we are no longer going to be entering the air).
; Hop backwards
[Statedef 105]
type = S
physics = S
ctrl = 0
anim = 105
sprpriority = 1
[State 105, 1]
type = VelSet
trigger1 = Time = 0
x = const(velocity.run.back.x)
y = const(velocity.run.back.y)
In order to remove the hopping behavior, you'll need to remove the y value here completely or set it to 0 to prevent KFM from going into the air.
[State 105, 1]
type = VelSet
trigger1 = Time = 0
x = const(velocity.run.back.x)
y = 0
Since we've removed the jumping behavior, you'll also need to adjust the triggers for the changestate to activate when the backdash is over (It would be best to change the animation for KFM's backdash as well (animation 105 in the air file) since it will no longer function as a hop and to match its new function (appearance-wise)).
[State 105, 3]
type = ChangeState
trigger1 = !Animtime
value = 0
We've adjusted the trigger here. When the animation has completed, the changestate will send us back to our standing state (0). You can adjust the x velocity of the backdash in the velocity section at the top of the .cns file by locating the velocity.run.back.x value.