would an alternative be to make the black scene change always append segments, instead of deleting existing segments? then you won't lose any existing segments when calling black scene

Yes, that's a good idea too. However, with the current implementation segments are created for the black scenes, instead of the non-blacks (which should be the normal case). So, everytime after running the "detect"-functionality I have to click on "invert all segments".
So, if you could by default create only segments for scenes with content then your solution for "from cursor position onward" would be perfect.

I've changed the black detect so that it searches only the interval defined by the currently selected segment

That works fine, thanks a lot!

However, as mentioned earlier, the "blacks" are segments instead of the scences with content. This results in having a mix of "content"-segments (e.g. manually created) and "black"-segments.

It threfore would be much better if you could have the content scences being created as segments.

I think you can now achieve your initial request of only detecting segments to the right of the cursor by doing this:

• Create a new segment starting from the cursor position and onwards towards the end of the video.
• make sure this segment you just created is selected
• Detect black scenes, now it will only detect to the right of the cursor (the current segment)
• now you can delete the original segment you created

If that's not what you want, I'm not sure what you exactly mean by "content segments" vs "black segments".

Your approach works fine for me.
What I mean by "content segments" vs "black segments": Lossless currently creates segments for the blacks (instead of the scences with actual footage, i.e. "a dog running"); this requires me to always "invert segments" so that I have segments with actual content.