SVG cursor themes is a new feature in Plasma 6.2, which we are really excited about. In this blog post, I would like to provide more background behind what motivated us to add support for them, wha…
If I recall correctly, GTK was initially against cursor-shape (because GTK prefers doing things client side), but is now opening to merging it. But not a high priority. The last discussion I found about it was from 5-6 months ago.
The linked article does a great job explaining the process of creating a theme assuming you have the SVG files. If you are asking how to create SVG files, then just use any vector editor (like Inkscape, for instance). You can find plenty of tutorials on how to create vectors through online video tutorials.