XYplorer Beta Club
The ability to make the leftmost column, and those sequentially next to it hold their position in spite of a horizontal scroll. Perhaps the '#' column at the very least, or '#' with the next column, perhaps holding a custom scripting button the filename, or whatever. This could also be implemented in such a way that a sticky column simply never scrolls past the leftmost or rightmost side regardless of how far the view is pulled.
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What I mean by a divided column view would be to have a movable line within a list window where columns to the left and right of it contained separate horizontal scroll bars. This would make it easy, for example, to have a particular view of say the filename or pathname on the left while scrolling various metadata or on the right. Or keep the line number, custom script button, and name in view while sliding right for other information. Currently, if many columns are chosen, even in horizontal view and rather fine print, it's rather hard to keep track of just which files are which once one gets scrolled off to the right. I at least would tend to use more columns if this were available, and gladly. And yes, in the way I envision it, one could see the same column on both sides of the split - the two sides would simply maintain the same line position but be different views into one column set.
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Another potentially useful function would be a scripting command that lines up a particular column to the left or right edge, or as far as possible in that direction. I could see myself flipping back and forth with shortcuts, for example.