Thanks for your replies, Jongware and David.
So I have found and replaced
(1) the folder “(Glyphs Panel Resources)” under “C:ProgrammeAdobeAdobe InDesign CS5Plug-InsText(Glyphs Panel Resources)”, and then I've also replaced
(2) “Glyphs Panel.apln” under the same location (ie., one step higher).
Both ways did not work: (1) did not change anything, (2) caused a crash (“would you like to tell Microsoft?” or something similar).
That means I have to manually look for and add the glyphs I use most often. Which leads me to a follow-up question: is there a nice way to do that?
Often I would have a Unicode code point (such as U+02BF) that I should add to the Glyph panel. Now in my view, browsing through the Glyphs panel and locating what you are looking for is a frustrating experience, given that there are so many characters (the presence of which, in turn, is a joyful experience, I hasten to add). It would be nice to just type in something like “02BF” and be presented with the character in the panel, and be able to add it to the the customized glyph panel.