[maxlin]

This kind of slider should ALWAYS have the middle part movable; IE grabbing it would move both handles at the same time.

For reference this is how Unity does it: https://docs.unity3d.com/StaticFiles/ScriptRefImages/EditorG...

[worthless-trash]

As a counterpoint, i would never have clicked the middle part, the current view in my mind was that this was a modified slider, not another new widget entirely.

"ALWAYS" might be a bit of an overstatement.