While this might be a slightly more complicated change, I think it would be
worthwhile to change gucharmap to only display on the right-hand side the
characters in the group(s) selected on the left.

Problems with the current approach:
- The pure number of characters currently displayed renders the scroll
handle mostly useless.
- The interaction between the left-hand pane and the right-hand pane
(scrolling on the right-hand side selects different items on the left)
feels awkward.
- The user doesn't get the feeling of "the right side displays what I
selected on the left" because of the additional characters displayed.

I think a better approach would be to only display the group(s) of
characters the user selected; "Basic Latin" could be displayed as a default
and ideally the latest selection would always be redisplayed the next time
gucharmap is run.

If deemed useful (and I think it would be a nice feature, if not very
difficult to implement) multiple selections could be allowed using the
standard multiple selection methods of lists (i.e. Control-click,
Shift-click, etc.); the different groups of characters could then either
simply be combined, or could otherwise be separated by small headers
displaying the names of the groups.