Sequence Editor: SHIFT+R, Remap Paths (also in pull down menu)
This allows to remap the root of a path to another directory.
Works on all selected Image strips. That way you can make absolute
paths relative, for example.
Example:
original path: /mnt/orange/finals/06_which_way/06_03b/
to be remapped: /mnt/orange/finals/
remap to: //
new path: //06_which_way/06_03b/