Thinking out loud here: Being able to click and drag (or swipe on a touch device) on the divider itself would be helpful.
And I agree with the comments that the divider itself doesn't provide enough of a visual cue about what's going on. I'd either go with the drop shadow suggestion, or play with a thicker divider that feels like a physical object.
And I agree with the comments that the divider itself doesn't provide enough of a visual cue about what's going on. I'd either go with the drop shadow suggestion, or play with a thicker divider that feels like a physical object.