Thank you Pilou.

So, I have discovered that in Windows 11, clicking on a file, there are 5 icons at the top of the dropdown list, including Cut, Copy, Rename, Share, and Delete, accessible WITHOUT clicking on "Show more options".
Windows 11 is currently displaying thumbnail of SVG file saved from a PDF.
The very annoying Windows 11 "news" popup in the lower left corner is now occurring. I was sure I disabled it a year or so ago...

SVGTrace online free conversion tool permits clicking on the various colors in the PNG, and will then convert curves to their corresponding color Layer (Like a Style in MoI). (lMy example has about 6 layers, including axis labels and values, with some colors the same for labels and one of the curve.)

Various color layers can then be deleted, and the conversion to SVG done. BUT the decolorized curves will still be SVG Imported into MoI. BUT, MoI will then create many more closed curves, including the desired Layer, in segments, some partly overlapping, making it easier to clean up the desired curve "pair".

MoI does NOT import color layers as Styles???

I wonder if Affinity Designer is good for editing SVG? It is "inexpensive".

- Brian