bug#57113: 29.0.50; Confusing icon customization interface

[Po Lu via "Bug reports for GNU Emacs, the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>]

Do "M-x customize-icon RET outline-open RET".

You will see the following interface:

INS DEL List:
            Choice: Value Menu Colorful Emojis
            Repeat:
            INS DEL String: 🔽
            INS
            Plist:
            INS
INS DEL List:
            Choice: Value Menu Monochrome Symbols
            Repeat:
            INS DEL String:  ⯆ 
            INS
            Plist:
            INS
INS DEL List:
            Choice: Value Menu Text Only
            Repeat:
            INS DEL String:  close 
            INS
            Plist:
            INS
INS
    State : STANDARD.

How to use this interface is not clear at all.  What does the first
level labeled "repeat" mean?  Why does it have multiple items, when it
is intended to represent a single icon?  What does it mean if I click
"INS"?  And if I click "DEL"?

Ignoring that, the individual items in the list are also badly
organized.  There is a menu of choices that seem to indicate the types
of the items in the value list (why it is a list is also unclear.)

Unfortunately, there is no help text in the menu explaining what the
individual icons mean, or what to do with the text or plist fields field
provided underneath.  The fields also don't update in response to
changes to the type, which doesn't make sense unless selecting "Images"
will automagically transform an Emoji symbol into an image.

The labels on the various fields should also be more informative than
"Repeat", "String" and "Plist"; those only tell you what the fields are,
and not what the fields do.

Thanks.