(please excuse my bad english, but i try my best
)
No, that doesn't work for me either.
But i "worked around". It always takes "Font0" for subtitles. But the bad thing with this is, that changing "Font0" to TrueType doesn't work (subs won't show up). So i just made a new font in Vis called "Subtitles". (It is a True Type Font, i chose "arial" for it as the TrueType font file, made it yellow, etc.)
Then i checked the "True Type font" option at "Font0". After that you can choose the "Subtitles"-Font as a (parent-)font for it. And then it shows the custom TrueType font for subtitles. yay.
For everything else choosing fonts works fine so far, so i think it is a good way to get a custom font for subtitles.