The sequence column, seen in Playing Now, and playlist views, is handy, and serves a purpose.
Although I don't use them much, the point of a playlist is that it keeps tracks in the order you want, usually, the order they are added.
If you apply a different sorting to the list, the sequence numbers are maintained so that the list can be easily returned to it's original order.
I believe that in Playing Now, the player will play tracks in sequence order, regardless of how the list is sorted at any given time during playback.
If you want the current order viewed to be preserved, simply select all tracks, right click, and use the "Update order" command. This will update the sequence number from 1 to x and until you change it again, this will be the new, preserved order of your tracks.
or am I missing something else here?
-marko