Classes can be marked for operations similar to the standard Emacs commands M-x tags-search and M-x tags-query-replace (see also See Tags-like Functions.)

M t

Toggle the mark of the line point is in or for as many lines as given by a prefix command. This command can also be found in the class' context menu.

M a

Unmark all classes. With prefix argument C-u, mark all classes in the tree. Since this command operates on the whole buffer, it can also be found in the buffer's object menu.

Marked classes are displayed with an > in column one of the tree display, like in the following example

     |> Collection
     |    IndexedCollection...
     |>   Set
     |    Dictionary