For the video output > filters > "subtitles" option which adds subtitles to the video, how do I increase the space between the subtitles and the bottom of the video? I want to "bump" the subtitles higher up in the video, as it's too far down for my liking. There are no options in the subtitles configuration area to do this.
Avidemux uses the libass library that can do such things.
Have you tried setting the margins in the configuration dialog?