Clever FFMprg Gui dull harfcoded subs

[sam12345]

What's the method to dull the harcoded sutitles to 70% in CFFMprg GUI

Like this


ffmpeg -i in.mp4 -vf "drawbox=x=0:y=ih-160:w=iw:h=160:color=black@0.35:t=fill" -c:v libx264 -crf 18 -preset slow -c:a copy out60.mp4

[ProWo]

Is already implemented for text subtitles.
Set background to 2 (50% transparent).
I'll implement a additional transparency control (from 0 to 100%).