Long story short, for internal trading videos updates i need to add a predone video cut to a lot of old videos. I need a way to not having to pass everyone one by one by premiere. Any software that could do that?
Assuming all your clips are the same format and dimensions:
Using FFmpeg, I think this would append the "ending.mp4" on to "file1.mp4" and save it as "output1.mp4":
ffmpeg -i "concat:file1.mp4|ending.mp4" -c copy output1.mp4
You can also do this using Adobe Media Encoder, but would take longer if you have many clips.