How to move subtitles up?

[Stanfoo]

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.

[AQUAR]

Avidemux uses the libass library that can do such things.
Have you tried setting the margins in the configuration dialog?