How to replace an orphaned external file by an existing one? (all instances) I used a video file in the VSE which is cut into many parts. 
When the project grew, I needed to reorganize the linked files. I renamed this video file. Now Blender doesn't see this file anymore.



In Motion5, there is a function "Replace Media" that lets you replace external files used in many strips by new ones for the whole project.

Does something similar exist in Blender by default or does anybody know a script that can do this?
You can set the filepath attribute on your sequences with python:

import bpy
for seq in bpy.data.scenes['Scene'].sequence_editor.sequences_all:
    if 'image_a' in seq.elements[0].filename:
        seq.elements[0].filename = "image_b.png"


You can optionally change the files location setting seq.directory if needed.