When hovering on the edge of a pane to activate the pane resize cursor, the area is currently only 2px wide, which is difficult to get without a relatively high degree of focus/patience, especially on a 4k monitor.
For reference, here’s how wide other resize edge areas are:
Windows 10 windows: 5px
Photoshop CC: 3px
Even a 50% jump up to 3px would help, but I think 4 or 5 might be the sweet spot. If this meant that the pane edges themselves would need to be a couple pixels fatter, to make it work without a ton of reprogramming, I think that’d be a fine trade-off. Just my 2c.