tcl tk 8.6.6 has a new busy command. The new tkinter library doesn't provide an interface for this command.

https://www.tcl.tk/man/tcl/TkCmd/busy.htm

The solution is to add to the class Misc of tkinter these methods:

def tk_busy(self, *args, **kw):
    self.tk_busy_hold(*args, **kw)
    
def tk_buy_hold(self, cnf=None, **kw)
    self.tk.call(('tk', 'busy', 'hold', self._w) + self._options(cnf, kw))

def tk_buy_configure(self, cnf=None, **kw):
    self.tk.call(('tk', 'busy', 'configure', self._w) + self._options(cnf, kw))
    
def tk_cget(self, option):
    return self.tk.call('tk', 'busy', 'cget', self._w, option)

def tk_busy_forget(self):
    self.tk_call('tk', 'busy', 'forget', self._w)

def tk_busy_current(self, pattern=None):
    if pattern is None:
        self.tk.call('tk', 'busy', 'current')
    else:
        self.tk.call('tk', 'busy', 'current', pattern)

def tk_busy_status(self):
    return self.tk.call('tk', 'busy', 'status', self._w)