Add option for MP4 output

I LOVE this program! It has made all my MKV problems disappear and manageable and is by far the EASIEST tool to use to add tracks to any sort of file. That being said, I can add an MP4/M4V file into here, add tracks and use the header editor and all that, but unfortunately the output will change the container into a Matroska file. While I understand (with this being "MKV"Toolnix) I would love to know if it would be possible to get a passthrough option, or a way to output MP4, or if this is something that is impossible to have happen. Thanks!

Welcome!

No, MP4 output will never happen. MKVToolNix is a program for creating Matroska files. It’s very good at that, and that is its intended scope.