mute option inside the midi key editor on Cubase LE 6

i compose songs on midi on cubase LE6 and when im inside the midi key editor cannot alow me to mute the track i’m in.
i dont understand why steinberg disable this function, because i use a lot and im shure im not the only one.
ive downloaded many cubase trial versions and i got the conclusion that they start doing this starting on cubase 6

can anyone tell me what cubase version has this funcion and what cubase version hasnt?