bug#36826: 26.1; request: add variable value editing feature to the *Help* buffer

[Drew Adams]

> > (`set-variable' does make the current value available
> > as the default (`M-n') for editing.  In other respects
> > `customize-set-variable' is preferable to `set-variable'.)
> 
> AFAICT: doesn't `customize-set-variable' prefill the minibuffer with
> the current value?

Seems to depend.  For `fill-column', yes.  For
`default-frame-alist' no.  You get a hint at
the beginning of the prompt: "[repeat]", but
you have no idea what to repeat, no completion,
etc.  You don't get the current value, as a
complex list etc., AFAICT.  (I haven't checked
the code, to see what it really does.)