I have a correction to what I said earlier. It seems that the use of the World 3D point is only a viable solution when the point is NOT being recalculated for each frame that is being drawn. In other words, it only works when there is a static 3D world point that stays in one place as you navigate around.
This means that there is no way to have the Legend be BOTH a 2D screen-oriented legend that remains in the plane of the screen as you navigate AND also have it not be repeated during larger screen captures. This fact seems to be designed into the way the Rhino DisplayPipeline works so I’m a bit doubtful that there’s anything that can be done on McNeel’s end to change this.
The only thing I can offer is a workaround with the 3D legend, which is a little bit more work to set up but it will look excellent in whatever screen capture that you make. All that you have to do is NOT use the 2D legend parameters and instead plug in a base_plane for the LB Legend Parameters. You can use the LB Orient to Camera component to get a plane that is oriented to the screen like so:
visualization_set_3D_screen_orient.gh (37.2 KB)
Your legend won’t stay in one place as you navigate around (you’ll have to re-compute the “Orient to Camera” component for it to get the latest screen orientation). However, it will not be repeated when you use and of the “Screen Capture” workflows (either with the Ladybug component or with the native Rhino command).
I hope this solution is good enough for your purposes since you’re hopefully only need to export such high res images when you’re putting together your final production-level deliverables. For quicker studies, you can just keep the viewport extents as they are and you’ll never see the legend repeated.