It could, but you should make sure that when your Timer regularly updates the slider value during the smoothing, that doesn’t trigger a sliderValueChanged() that in turn interferes with the smoothing currently in progress.
Also, an issue that I see is this: suppose you’re at max value and you set to min. Before the smoothing Timer kicks in and starts decreasing the value from max to min, the Slider will have assumed the min value for a small time interval, effectively causing its value to jump from max to min as a result of your change, then abruptly to brought back to max again by the smoothing Timer which will decrease it back to min again.
The initial jump from max to min and then back to max sounds like something you’d like to avoid, preferring the value to stay at max and then decreasing towards its intended target min value by effect of the Timer only. but I cannot imagine an easy way to obtain that