Two more pieces of evidence that there is a problem with tkinter/tk8.6 on Mac.  On #34120, Vlad T. confirmed the misbehavior on 3.5 compiled for 8.6.  #34281 reports another problem with an editor subwindow on 3.7 Mac.

There are now 4 issues about some IDLE feature failing specifically on MacOS with tcl/tk 8.6.8.  (All but 1 with 3.7.0.)
#34047: editor scrollbar slider 'sticks' at bottom
#34120: freeze when closing config and about dialogs
#34281: (new today) wrong window activates when closing "Go to Line" box
#34275: (this issue) calltips do not appear

The editor scrollbar was touched last May.  The config and about dialogs contents were edited last summer.  But the calltip and and goto code is essentially untouched for 2 years.

I am changing the title from 'IDLE: no calltips on MacOS with tk 8.6' and adding tkinter as component and Serhiy as Nosy.

I have never used a Mac, but I have available a 2012 MacBook Air, which I just upgraded to current High Sierra 10.13.6.  I intend to install 3.7, confirm the bugs, and try to find simpler failing examples.  But I cannot patch _tkinter, let alone tcl/tk.