With more debugger use experience, I decided that there are many possible small improvements that would make it easier to use for beginners.

0. The window strikes me as overall 'blah', if not ugly. The difference between inactive and active could be brighter.

1. There are 5 action buttons: They could be labelled as such, and maybe spaced out a big.  They could all use an explanatory popup.  [quit], for instance, means quit the current session *without* closing the window.

2. There are 4 display checkboxes. They could be labelled as such on a line under the action buttons. The buttons could then be spread out a bit.

3. In the middle of the gray field, I see, for instance,
  tem.py:1 <module>0  # or
  <pyshell#0>:1 <module>0  # if enter statement interactively
'tem.py' is the file name, either 0 or 1 or both are line numbers (Python 0, tk 1). <module> seems redundant here as nothing else can be run,  unless importing another module in an open window would 

4. The first line in the Stack box (not labelled, unlike Locals and Globals boxes), always has 
'bdb'.run(), line 431: exec(cmd, globals, locals)
This seems like noise, better suppressed if possible. Next line:
>'__main__'.<module>0, line 1: pass

5. If one only has [locals], globals == module-level locals is displayed in a 'locals' box. If one hits [globals], that box is relabeled 'globals' and an empty 'locals' box open above.  Perhaps the initial box should be 'globals/locals' and relabeled to either when stepping into a class or function.