Катя Москальчук

Можно менять параметры через метод configure. Текущий параметр можно достать отсюда: txt.config()['show'][-1]

from tkinter import *  


def show_password():
    
    current_state = txt.config()['show'][-1]

    if current_state == '*':
        txt.configure(show='')
    else:
        txt.configure(show='*')


window = Tk()  
window.title("title")  
txt = Entry(window,width=10, show='*')
txt.grid(column=1, row=0)  
btn1 = Button(window, text="Показать пароль", command=show_password)  
btn1.grid(column=3, row=0)  
window.mainloop()

import tkinter as tk

root = tk.Tk()

def myfunction(*args):
    l = 6
    check_entry = stringvar1.get()
    if len(check_entry) >= l:
        button.config(state='normal')
    else:
        button.config(state='disabled')

stringvar1 = tk.StringVar(root)
stringvar1.trace("w", myfunction)

entry1 = tk.Entry(root, width=15, textvariable=stringvar1)
entry1.grid(row=1,column=1)

button = tk.Button(root,text="submit", state='disabled')
button.grid(row=1, column=4)

root.mainloop()