When dragging the sash to split an editor window (which is a great feature), the contents of the visible panes scroll in an unpredictable, and very unhelpful way.

When moving the sash to/from the top of the window, the contents of the lower pane scroll unpredictably.  Every time I use this feature, I have to get my bearings all over again, and *always* have to scroll the bottom pane because what is visible has changed.

I believe the behavior should be fixed so that dragging the sash doesn't cause any change to what is already visible on the screen (with one exception -- described below).  When moving the sash from the top to bottom, more of the buffer content is shown in the upper pane (farther to the end of the buffer, leaving the top of the upper pane anchored where it is) , and less of the buffer content is shown in the lower pane (less from the beginning of the buffer, leaving the bottom of the lower pane anchored where it is).

Extending this behavior to the removal of the sash, so there is only a single pane left: when dragging the sash off the top of the window, the bottom of the lower window remains anchored and more of the buffer is shown toward the beginning as the sash is moved upward; when dragging the sash off the bottom of the window, the top of the upper window remains anchored and more of the buffer is shown toward the end as the sash is moved downward.

The exception would be if there is insufficient content in the buffer to make more/less of it visible as the sash is repositioned as described above.  In that case, the content would scroll so the visible area remains as full as possible.

Please consider this -- what is an exceptional feature has been reduced to being marginally valuable because its behavior is unpredictable and disorienting.