When I 1st learned the 8000, I was shown the CUEUP&PLAY portion of the DEVICE menu - that's apparently what is mostly taught to people, as it works for most operations: the TIMELINE menu was almost taught to me as an afterthought. But I tend to work in the TIMELINE menu most often, and it's here that you'll find the Variable Speed function that you are asking about. (1) In the TIMELINE menu, select the START button, then Start TC SET & enter the timecode that you want it to start at. (2) Press the REWIND ACTION BUTTON - select CUEUP & enter the timecode that you want the device to cue to before playing (this should be the same code as for the START command). I often find that the CUEUP button won't light at 1st. So I press the START button next to it & enter the code (& press Rewind Action Set), then I find I can press CUEUP & Rewind Action Set. Pressing either PREV or TIMELINE will take you back to the Timeline menu. INSERT this as your 1st keyframe. So what you have just done is pretty much what you would do in one simple step in the CUEUP&PLAY menu. That's why CUEUP&PLAY is often the preferred way of setting start/stop values - it's much less involved than the TIMELINE menu. (3) Now in the Timeline menu, press either the Variable Speed SET button (to enter a specific speed via the 2nd soft knob) or FIT. As I recall, FIT takes the difference between the START & STOP timecodes & compares this value to the keyframe duration to generate a playback speed automatically. But entering a variable speed manually may suit your purposes better.