This should be done by decoupling the roweditor from the segment grid.

As an effect it will be possible to open a segment and scroll through the complete table with the segment still open. The segment will be opened at the same place of the screen always for any segment. The final position of the editor should be evaluated by testing, a good starting point would be a top position in the grid on 25% of the overall grid height.
The segment opened in the grid will be placed behind the roweditor - but will be able to scroll in sight, when the user scrolls.

When the user opens another segment, the editor scrolls automatically the opened segment in the grid to be positioned behind the roweditor.