In my 2015 S4 6MT I had a stainless clutch line installed a few years ago and I'm pretty sure that's the point when the car became more difficult to shift. And it may be placebo but it seems like the clutch doesn't fully disengage unless I get the pedal all the way down to the floor. One indicator of this (I think??) is that when I am looking at the instantaneous gas mileage readout, if I shift 'normally' as far as clutch pedal travel is concerned, the readout does not change when I shift; however if I very deliberately push the pedal literally as far as it will go, the readout will momentarily go to ' - - ' (no reading) while I shift, and then resume reading out a value when I get into the next gear.
I have also notice that there is apparent lag in the throttle response, regardless of drive select mode, when I start to give it gas while letting the clutch pedal out, i.e. when starting out in 1st gear from a stop. I am wondering if the ECU is reading the clutch position from the Hall effect sensor in the master cylinder (and someone please correct me if I am making any of this up) and it's not getting the reading it wants, thereby affecting throttle response? This may also be placebo but it seems that if I very deliberately mash the clutch as far as it will go (hurting my foot) then the throttle response is more immediate as I would expect it to be - but if I start out with the clutch pedal in a more normal position applying a civilized amount of force to it, i.e. not putting a dent in the floor board, this throttle hesitation exists.

So - I've been dealing with it for a few years and it really saps the driving experience. Any idea whether the extended slave cylinder would solve any of these issues? Or does this sound indicative of hydraulic lines that need to be bled? Or Both?

To clarify, I have never experienced the "push to start" issue, and all things considered I don't wail on this car so at 76k miles currently I doubt the root issue is a worn/failing clutch, also considering that these symptoms started at around 40k miles.