It could be helpful to auto-tag with <abbr></abbr> tags:
func1(a, b, <abbr title="Parameters before the slash (/) are positional-only.">/</abbr>)
> func2(<abbr title="Parameters following the star (*) are keyword-only.">*</abbr>, kwarg1, kwarg2)
Rendered:
func1(a, b, /)
func2(*, kwarg1, kwarg2)
*args and **kwargs could also be tagged, although those are more likely to be addressed in the body of the docstring.
I have no idea how helpful/annoying large numbers of <abbr></abbr> tags are for screenreader users, but I find the dotted underline is the right level of ignorable-at-will for things like this that are helpful to have at hand until the shorthand becomes familiar.