For future reference: an exception is not a crash.  A crash is a core dump or the Mac equivalent.

Anyway, I also cannot reproduce with Python.org python on my Macbook.
  python 3.7.3(v3.7.3:ef4e...) Mar 25, 2019 16:52:21
  Clang 6.0 (...) on Darwin
Where did you get your Python installer?  Did it include tck/tk?  If not, perhaps python3.exe and the tcl/tk being used do not match.

Does IDLE work at all?  Can you click Help and About IDLE?  If so, what is the tk version? 

I used the pad to move the cursor over the scrollbar slider, held my left finger down on the left side of the pad, and moved the slider and file display with my right finger.  Is this what you did?

From the traceback it appears that the exception occurred in the C code of  _tkinter or more likely, the C code of tcl/tk, before any of IDLE's python-coded event handlers are called.  Hence, Ned's comment.