How to edit rendering profiles on Synology DS211j?

I can't get my subtitles to work with mkv files. I tried everything. They work with avi files, but it seems that the Panasonic Viera (my tv model also) profile doesn't want to parse *.srt subtitles with mkv files.

Can anyone please guide me (preferably step by step) how to edit my panasonic profile? I think i might need to edit the SubtitlesMimeType definition.

Thanks for your help in advance.

[zip]

I think it has been discussed that the TV doesn't play external srt for mkv files for some reason. Search in the Panasonic forum.