Hi Jean-Paul - it's kind of hard to have a slider for distance values that are scale dependent.

For Blend it works more easily because the blend value is a kind of "scale factor" and not just a direct distance value.

For values that represent a distance, it's hard to decide what the lower and upper bounds should be for the slider range, because the values you may want to use are more dependent on the scale of the object you are working on.

- Michael