vdr-plugin-ttxtsubs

Is this intented to be integration like adding teletext subtitles into the subtitles menu (in which is DVB-subtitles at the moment)?

I think this feature would be good to have, I got this idea as there exists some channels (Canal digital, Thor 1W) have both DVB- and teletext subtitles, and at the moment both of them are displayed, if not to disable one or another.

Yes. The long term goal is to integrate ttxtsubs side by side with the DVB subs in VDR. But don't expect this to happen any time soon.