Hello @Fam
It was more difficult than I think...
At first, I found that the <div> tag of slider circle handle has attribute "aria-valuenow", so I tried to change its value using action "Run JavaScript function on web page", but I had not succeeded.
So I decided to change the approach, and try to drag the slider handle with the mouse.
For now, I need to know the coordinates (X, Y) of the UI element.
Referring to the documentation below, I was able to get them:
Get the coordinates and size of a web element - Power Automate | Microsoft Docs
To emulate the drag operation of mouse, I used actions below:
"Move mouse (to the X, Y coordinates of UI element)"
"Send mouse click (Left button down)"
"Move mouse (increase X value to move it to right direction)
"Send mouse click (Left button up)"
It's not beautiful, but it worked anyway...
Screenshots of my example flow:


As a result, I could change the min value of "Tot. Rev ($M)" by moving the slider handle 200 pixels to the right from its initial position:

However, as you may have already noticed, the minimum / maximum value of the slider varies depending on each item, so you have to calculate how much you need to move the mouse left and right in order to set it to the target value. Also depending on the environment of the machine that is running this flow, the position and scale of X and Y may change.
In my personal opinion, it can be difficult to develop a flow having production quality with above approach...
Thank you.