Adding to video sources. (Extra audio tracks, subs, etc)

[TERMINATOR461997]

This may be a dumb question, but I cant seem to get Fastflix to add an audio track to a project. For example, I'm working on adding Japanese audio and English subs to a AV1 video, but Fastflix just spits out a warning about it not being a video file. Is there something I am missing here?

Going through command line ffmpeg is very annoying to do, since there is no complete list of the commands and what they do that I have found. Most are the basics, and the documentation doesn't list the commands in a easy way to locate the command for what your trying to do. (Feel free to correct me)

[cdgriffith]

Currently there is no way to merge multiple files into a single one with FastFlix, would be a great feature but a lot of work