Seems like a nice feature in an upcoming release. Ive actually tried to make a script myself, but I cant really get my head around it.
Atm I have 2 anchors, one anchored to the right edge of the widget placed on the left side off the screen, and the other one is anchored to the left edge of the sprite placed on the right side of the screen.
I can get the distance between those, but I cant figure out how to convert it to a correct localscale.x-value on my sliced sprice between them... Would appreciate some kind of input or help!