Vehicle Clutch Input

So hey guys.
im breaking my head over this one.
Ue4’s vehicle has axis throttle, axis brake, axis clutch. The problem here is. there is no way for me to set
the clutch, in the “vehicle movement component” theres under the mechanical setup under transmission a clutch strength. That is the value i would need to manipulate. But it seems out of reach for me…
Could anybody give me a hint on how to edit this apperently not editable value?

Thank you in advance!