This was our compromise for the grid column menu fix so that it doesn't get clipped/blocked by the panel borders. See issue here: https://www.labkey.org/home/Developer/issues/issues-details.view?issueId=45139
We could likely add more code to try and handle the "move the menu along with the scrolled window", but we decided not to take on that part as part of 45139. Nick, I think you did something along those lines with the original editable grid cell lookup (before we switched to using the SelectInput for those). Do you have an estimate for this scroll tracking work?