This month on "Stealing ideas from the VsCode release notes":

We don't yet support resizing panes with the mouse (that's #992). We also don't support configuring the pane border color (that's #3061 / #3327).

BUT WHEN WE DO, it would be cool to have a configurable color for the hover on the pane borders. So you would know when you've got a pane border hovered, and that it's actionable.

Also neat would be if it had that Fluent "glow"? though I suppose "reveal focus" is "xbox only", so maybe not that.