Should I mark my question as a duplicate or delete it?
I think you should vote to close it as a duplicate which I think should take effect immediately.
That way it becomes another signpost to the same answer.
Perhaps there was a reason you did not find the other question.
So, besides what @PolyGeo answered, I suggest always try editing the duplicate question for readability and searchability (title, body and tags) if one thinks it is appropriate.
For example, usually titles starting with:
- In QGIS plugin, ... or
- How do I ...
are not the best for distinguishing content through searching.
Here is a Meta SE Q/A with hints for writing titles: How do I write a good title?*
*Ironically, the title is not following its own guidelines, but it is a useful post anyway.