import tkinter as tk
from tkinter import ttk
class Main(tk.Frame):
    def __init__(self, root, *attr, **kwargs):
        super().__init__(self, root, *attr, **kwargs)
        self.init_main()
    def init_main(self):
        toolbar = tk.Frame()
        toolbar.pack(side=tk.TOP, fill=tk.X)
        toolbar.config(bg='#d7d8e0', bd=2)
        btnOpenDialog = tk.Button(toolbar, text='Добавить позицию', command=self.open_dialog)
        btnOpenDialog.pack(side=tk.LEFT)
        btnOpenDialog.config(bg='#d7d8e0', bd=0, compound=tk.TOP)
    def open_dialog(self):
        Child()
"""
class Child(tk.Frame):
    def __init__(self):
         = tk.Toplevel()
        .title('Добавить доходы/расходы')
        .geometry('400x220+400+300')
        .resizable(False, False)
"""
if __name__ == "__main__":
    root = tk.Tk()
    my_widget = Main(root)
    Main.pack()
    root.title("Домашние финансы")
    root.geometry("650x450+300+200")
    root.resizable(False, False)
    root.mainloop()