Feature request: position of subs in Subtitles plugin Filter

[cachaito]

Hi! Instead of the Margin Top and Margin Bottom options (btw, both existing Margin options only take 2-digit values and are worthless if you want to use them to position text in a 16:9 aspect ratio), I think it would be better to use one field that can position subtitles by given pixels (or percentage) from the top. Why? Currently, if you add black borders to a video and set the video to 1920px resolution, the added subtitles will be mismatched and will not be able to be adjusted accordingly. Example in the attached screenshots: