FWIW: I let Slope mode do as much as possible automatically and use gear changes in rare circumstances. It is like a proper race sprint: You pick your gear and pedal all out until the finish line. Need more power? Pedal faster. Want to always win the sprint? Hope your competitors change gears in mid sprint.
Indoors, I set a target power goal for 80 rpm at let’s say 900w. If pedal faster, I will hit 1000w. Slower - or near the the end of a short interval - I might hit 800w. If my interval repetition is designed right, I will be able to just hold 900w on the last interval in the set.
Changing gears makes it harder to plan the next set of intervals with desired progressive resistance. If I don’t know the gear, it becomes harder to create the best next power target. I could write an algorithm to integrate cadence and power to get gear. I avoid that because sprint training is about hitting maximum power at optimal cadence without changing gears. Keeping the gear fixed, makes things simpler - and teaches good habits.
BTW: Changing settings on the screen will not work for me. Touching the screen during a sprint is virtually impossible. I use Erg mode during recovery segments. This means I can’t make level changes until the slope mode sprint has started.