how do i find the fader in the arrange window

once by accident i pulled up a volume fader while mousing around in the arrange window just to the right of the box that has s m w r etc buttons. i would love to find this again but i have tried all combinations of right click control click etc. anybody know where i find this feature? thank you

found it btw. it is only an option on a group channel. wish it were on the rest.