This is one way to do what you want.
Go to File Open MLT XML as Clip.
Once the mlt is loaded it will be in the source player. Add it to the playlist. Do this for each video you want to export. You can save the mlt as Jobs. That way it can be used again.
Export all the videos in the playlist using the export From Each Playlist item function. All the videos in the playlist will export and be numbered sequentially. The export format will be the same for all the videos.
If you export from playlist all the videos in the playlist will be concatenated.