Ok, thank you for the advice, and is it also the case that if the chain is on a small tabletop, you can use one half-speed, and if on a large tabletop, you have as many as four of these half-speeds at your disposal?
I don't really need the trim feature as I never really get chain rub. I use the "gear protection" feature to avoid cross chaining so the RD will avoid the two most extreme opposite gears of the respective chainring. The way I understand the trim feature is that whenever you press the button of the chainring that you're already in, the FD will reposition itself depending on the gear you're in at the back. So the more extreme you're cross chaining, the bigger the adjustment that the FD will make if you use the trim feature. But that's just my observation.
But like I said: Since I never get chain rub, I don't really bother to use the trim feature. I just shift the front when I have to.
