On Mon, 01 Nov 2021 16:29:42 +0200 Eli Zaretskii <eliz@gnu.org> wrote:

>> Date: Mon, 01 Nov 2021 21:52:17 +0800
>> From:  Po Lu via "Bug reports for GNU Emacs,
>>  the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>
>>
>>
>> Run emacs -Q.  Do M-x customize-group RET files RET, expand "After Save
>> Hook", then click "INS" twice.  The second INS button will not have a
>> left box line, which is visually inconsistent with the first, and with
>> how buttons work in general across all X-Windows applications.
>
> I cannot reproduce this.  Maybe this is specific to GTK?

I see this on a no-toolkit build as well as a Gtk build.  For me, it
suffices to click "INS" once, see attached screenshot.

Steve