This is an index issue for keeping track of improvements to IDLE's class browser.  They should mostly (or all?) be done in separate issues and PRs.  

Existing issues with patches.  Only the first, a 'must', is recently reviewed.
#1612262  Use 3.7 enhanced pyclbr to show nested classes and functions.
#6171   Obsolete problem but patch may have useful idea.
#20827  Display function arguments (would be nice).
#25090  Remove most icons (also applies to pathbrowser).

New 'must' issues that need patches.
#31459  Rename ClassBrowser as ModuleBrowser
#31460  Redo signature of ModuleBroser.__init__.

Other potential issues, most of which also affect pathbrowser.
Make broswers scrollable with mouse.  (See turtledemo for how.)
Start browsers with bigger window.
Clicking of module in pathbrowser should open module browser.
Separate toplevel window from browser frame.
Search tree (including items not visible) with status bar box.
Utilize ttk.Treeview in browsers.

Browsers currently use idlelib.tree.TreeWidget.  Treeview is not a drop-in replacement because TreeWidget has some of the higher-level app-specific functions that users are expected to add to Treeview.  But could Treeview replace the low-level parts of TreeWidget that actually display stuff on the screen?

Us

#31552 ttk.Treeview

I was sitting down to write a patch for #31459, when I discovered yours.  If you want to write more module brower patches, such as for #31460  I will do something else.

#25090 opened with a broad discussion of module broswer and code context, but I focused it on removing the folder and file icons misused for classes and functions in Module Browser.  Above, I suggested possibly changing pathbrowser, but I have decided against that.  The patch will be trivial, so I am going to do it and see what I think.

Sorry about that.  You can do 31460 if you want.  I haven't started it.

Whoops, patching tree.py to not use icons is not trivial.  See new comment on #25090.

#37902 Add mousewheel scrolling.