The plot package already contains examples for every type of plot. Documentation can always be improved, but I think the problem here is that the plot package is composable and is integrated well with the other libraries such as pict and the draw library. This is normally a great thing, but it is a problem for new users, since they expect a specific function for every feature they could possibly want.
For example, presumably the author searched the documentation for "plot inside plot", and even though they knew that one can create a plot as a pict using plot-pict and one can place any pict on a plot using point-pict, it did not occur to them to combine the two to place a plot inside a plot.
What could be done is a "cookbook" style documentation/website, where specific examples are added, similar to what matplotlib does: Examples — Matplotlib 3.5.1 documentation. However I don't have time to start and maintain such a project. For my part, I wrote several plot-related blog posts, to illustrate its flexibility, and I might add some more examples in the future there. I will also attempt to answer specific examples when people ask for these types of questions on the forums.
Alex.