A neat small feature Sony Vegas has is that if you take a mp4 file and “open as” with vegas.exe, it will open a project with a project profile matching that clip. Kdenlive only seems to open project files directly.
As far as I know Kdenlive already has this. See GIF
I think they are talking about opening a file via a right click, open as not dragging it into the program. I just tried it and when you try to right click it will try open the file as project file.
Niether, I think the original poster by the sound of it is talking about right clicking the file in dolphin etc open with-> kdenlive. But until they chime in again we won’t really know what they were trying to say.