>>>>> In <b4mu0h6l5s1.fsf@jpl.org> Katsumi Yamaoka wrote:

>>> I'd like to propose adding two features.  The following
>>> definition displays all the MIME buttons even if
>>> `gnus-inhibit-mime-unbuttonizing' is nil (which is the default),
>>> and specifies which part the user is going to manipulate.

I revised the function I posted last.  This does:

issue the error if the article is not visible or the article
doesn't display the right contents or there's no specified part.

point the cursor and the arrow at the MIME button when the
handler function (e.g., `2 K d', `2 K O', `2 K |', etc.) prompts
the user for something.

redisplay the article so that all the MIME buttons might be
visible if the part which doesn't have the MIME button is
selected.

Could you test it?  I added an article for testing in the
gmane.test group as <b4mbr3dxsxj.fsf@jpl.org>.